[chore] Implement chloggen fragment automation for releases (#2787)

.chloggen/TEMPLATE.yaml

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+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type:
+# The name of the component (e.g. jmx-metrics, resource-providers, aws-xray)
+component: 
+# A brief description of the change.
+note:
+# One or more tracking issues related to the change. Use the PR number if no issue exists.
+issues: []
+# Optional additional context.
+subtext:
+# 'user' if relevant to end users, 'api' if there is a library API change.
+change_logs: [user]

.chloggen/config.yaml

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+change_types:
+  - breaking
+  - deprecation
+  - new_component
+  - enhancement
+  - bug_fix
+entries_dir: .chloggen
+changelog_md: CHANGELOG.md
+template_yaml: .chloggen/TEMPLATE.yaml
+change_logs:
+  user: CHANGELOG.md
+default_change_logs: [user]

.chloggen/pr-2837.yaml

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+change_type: enhancement
+component: 
+note: Automate changelog generation using fragment pattern
+issues: [2787]
+subtext: 
+change_logs: [user]

.github/workflows/changelog-fragment.yml

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+name: Changelog Fragments
+
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - labeled
+      - unlabeled
+
+permissions:
+  contents: write
+  issues: write
+  pull-requests: write
+  models: read
+
+jobs:
+  generate-fragment:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.head_ref }}
+          token: ${{ github.token }}
+          fetch-depth: 0
+
+      - name: Install yq
+        run: |
+          go install github.com/mikefarah/yq/v4@v4.44.3
+
+      - name: Check skip conditions
+        id: skip
+        env:
+          PR_TITLE: ${{ github.event.pull_request.title }}
+          PR_LABELS: ${{ toJson(github.event.pull_request.labels.*.name) }}
+          PR_USER_LOGIN: ${{ github.event.pull_request.user.login }}
+        run: |
+          skip=false
+
+          if [[ "$PR_USER_LOGIN" == "dependabot[bot]" || "$PR_USER_LOGIN" == "renovate[bot]" ]]; then
+            skip=true
+          fi
+
+          if [[ "$PR_TITLE" == \[chore\]* ]]; then
+            skip=true
+          fi
+
+          if jq -e 'index("Skip Changelog")' <<<"$PR_LABELS" >/dev/null; then
+            skip=true
+          fi
+
+          echo "skip=$skip" >> "$GITHUB_OUTPUT"
+
+      - name: Check existing fragment
+        id: fragment
+        env:
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          fragment=".chloggen/pr-${PR_NUMBER}.yaml"
+
+          if [[ -f "$fragment" ]]; then
+            echo "exists=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "exists=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Fetch base branch
+        if: ${{ steps.skip.outputs.skip != 'true' && steps.fragment.outputs.exists != 'true' && github.event.pull_request.head.repo.full_name == github.repository }}
+        run: |
+          git fetch origin "${{ github.event.pull_request.base.ref }}:refs/remotes/origin/${{ github.event.pull_request.base.ref }}" --depth=1
+
+      - name: Generate fragment
+        if: ${{ steps.skip.outputs.skip != 'true' && steps.fragment.outputs.exists != 'true' && github.event.pull_request.head.repo.full_name == github.repository }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          PR_TITLE: ${{ github.event.pull_request.title }}
+          PR_BODY: ${{ github.event.pull_request.body }}
+          BASE_REF: ${{ github.event.pull_request.base.ref }}
+        run: |
+          changed_files="$(git diff --name-only "origin/${BASE_REF}"...HEAD)"
+
+          request_payload="$(jq -n \
+            --arg title "$PR_TITLE" \
+            --arg body "$PR_BODY" \
+            --arg changed_files "$changed_files" \
+            '{
+              model: "gpt-4o-mini",
+              response_format: {type: "json_object"},
+              messages: [
+                {
+                  role: "system",
+                  content: "Generate a single JSON object for a changelog fragment. Return only valid JSON with these keys: change_type, component, note, issues, subtext, change_logs. change_type must be one of breaking, deprecation, new_component, enhancement, bug_fix. component must be blank if the PR does not clearly map to one component. note must be a brief end-user facing summary. issues must be an array of issue numbers without #. subtext is optional and may be null or omitted. change_logs must be [\"user\"]. Do not add markdown or extra keys."
+                },
+                {
+                  role: "user",
+                  content: "PR title: \($title)\n\nPR body:\n\($body)\n\nChanged files:\n\($changed_files)"
+                }
+              ]
+            }')"
+
+          response="$(curl --fail-with-body --silent --show-error https://models.github.ai/inference/chat/completions \
+            -H "Accept: application/vnd.github+json" \
+            -H "Content-Type: application/json" \
+            -H "Authorization: Bearer ${GITHUB_TOKEN}" \
+            -d "$request_payload")"
+
+          jq -r '.choices[0].message.content | fromjson' <<<"$response" | "$(go env GOPATH)/bin/yq" -P - > ".chloggen/pr-${PR_NUMBER}.yaml"
+
+      - name: Validate AI Output
+        if: ${{ steps.skip.outputs.skip != 'true' && steps.fragment.outputs.exists != 'true' && github.event.pull_request.head.repo.full_name == github.repository }}
+        env:
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          fragment=".chloggen/pr-${PR_NUMBER}.yaml"
+
+          if ! "$(go env GOPATH)/bin/yq" -e 'has("change_type") and has("component") and has("note")' "$fragment" >/dev/null; then
+            echo "missing required keys: change_type, component, note"
+            rm -f "$fragment"
+            exit 1
+          fi
+
+      - name: Commit
+        if: ${{ steps.skip.outputs.skip != 'true' && steps.fragment.outputs.exists != 'true' && github.event.pull_request.head.repo.full_name == github.repository }}
+        env:
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          PR_BRANCH: ${{ github.head_ref }}
+        run: |
+          git config user.name opentelemetrybot
+          git config user.email 107717825+opentelemetrybot@users.noreply.github.com
+          git add ".chloggen/pr-${PR_NUMBER}.yaml"
+          git commit -m "Add changelog fragment for PR #${PR_NUMBER}"
+          git push origin HEAD:"${PR_BRANCH}"
+
+  validate-fragment:
+    needs: generate-fragment
+    if: always()
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.head_ref }}
+          token: ${{ github.token }}
+          fetch-depth: 0
+
+      - name: Check skip conditions
+        id: skip
+        env:
+          PR_TITLE: ${{ github.event.pull_request.title }}
+          PR_LABELS: ${{ toJson(github.event.pull_request.labels.*.name) }}
+          PR_USER_LOGIN: ${{ github.event.pull_request.user.login }}
+        run: |
+          skip=false
+
+          if [[ "$PR_USER_LOGIN" == "dependabot[bot]" || "$PR_USER_LOGIN" == "renovate[bot]" ]]; then
+            skip=true
+          fi
+
+          if [[ "$PR_TITLE" == \[chore\]* ]]; then
+            skip=true
+          fi
+
+          if jq -e 'index("Skip Changelog")' <<<"$PR_LABELS" >/dev/null; then
+            skip=true
+          fi
+
+          echo "skip=$skip" >> "$GITHUB_OUTPUT"
+
+      - name: Exit if skipped
+        if: ${{ steps.skip.outputs.skip == 'true' }}
+        run: exit 0
+
+      - name: Validate fragment
+        env:
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+        run: |
+          fragment=".chloggen/pr-${PR_NUMBER}.yaml"
+
+          if [[ ! -f "$fragment" ]]; then
+            echo "❌ Missing changelog fragment: $fragment"
+            echo "If you are contributing from a fork, you must create this file manually."
+            echo "Copy the contents of .chloggen/TEMPLATE.yaml into a new file named $fragment, fill it out, and commit it to your branch."
+            exit 1
+          fi
+
+          go install go.opentelemetry.io/build-tools/chloggen@v0.15.0
+          "$(go env GOPATH)/bin/chloggen" validate --config .chloggen/config.yaml

.github/workflows/draft-release-changelog.yml

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+name: Draft Release Changelog
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Release version (e.g. 1.57.0)'
+        required: true
+        type: string
+
+jobs:
+  draft-changelog:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Validate version input
+        run: |
+          if [[ ! "${{ inputs.version }}" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+            echo "❌ Invalid version format: ${{ inputs.version }}. Must be X.Y.Z"
+            exit 1
+          fi
+
+      - name: Install chloggen
+        run: go install go.opentelemetry.io/build-tools/chloggen@v0.15.0
+
+      - name: Dry run (preview)
+        run: $(go env GOPATH)/bin/chloggen update --dry
+
+      - name: Compile changelog
+        env:
+          VERSION: ${{ inputs.version }}
+        run: $(go env GOPATH)/bin/chloggen update --version "$VERSION"
+
+      - name: Create PR for Release Captain review
+        uses: peter-evans/create-pull-request@v6
+        with:
+          # Strictly require the bot token for EasyCLA compliance
+          token: ${{ secrets.OPENTELEMETRYBOT_GITHUB_TOKEN }}
+          commit-message: "[chore] update changelog for release ${{ inputs.version }}"
+          committer: "opentelemetrybot <107717825+opentelemetrybot@users.noreply.github.com>"
+          author: "opentelemetrybot <107717825+opentelemetrybot@users.noreply.github.com>"
+          title: "[chore] update changelog for release ${{ inputs.version }}"
+          body: |
+            Automated changelog compilation for release `${{ inputs.version }}`.
+
+            **Release Captain:** Review the entries below, make any manual corrections, then merge.
+          branch: "chore/changelog-${{ inputs.version }}"
+          base: main