Add GitHub Actions workflow for PHP 7.4 downgrade and tagging

- Introduced a workflow to automate downgrading code to PHP 7.4 using Rector.
- Added steps to verify PHP 8.2 compatibility before initiating the downgrade.
- Implemented tagging strategy for `v1.x.y` releases from `v2.x.y` tags.
- Updated Composer constraints for PHP 7.4 compatibility.

Author: georgedeploy

.github/workflows/downgrade-php74.yml

@@ -0,0 +1,115 @@
+name: Release and Downgrade to PHP 7.4
+
+on:
+  release:
+    types: [published]
+
+permissions:
+  contents: write
+
+jobs:
+  verify-php82:
+    name: Verify PHP 8.2 Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Ensure release tag starts with v2.
+        run: |
+          TAG="${{ github.event.release.tag_name }}"
+          echo "Release tag: $TAG"
+          if [[ ! "$TAG" =~ ^v2\.[0-9]+\.[0-9]+$ ]]; then
+            echo "This workflow only runs for v2.x.y release tags. Got: $TAG" >&2
+            exit 1
+          fi
+
+      - name: Setup PHP 8.2
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          coverage: none
+          tools: composer:v2
+
+      - name: Install dependencies
+        run: composer install --no-interaction --prefer-dist --no-progress
+
+      - name: Run checks (cs, psalm, tests, type, coverage, mutate)
+        env:
+          XDEBUG_MODE: coverage
+        run: |
+          composer validate --strict
+          composer cs
+          composer sca
+          composer test
+          composer type
+          composer coverage
+          composer mutate
+
+  downgrade-and-tag:
+    name: Downgrade to PHP 7.4 and Tag v1.x
+    needs: verify-php82
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out php7.4 branch
+        uses: actions/checkout@v4
+        with:
+          ref: php7.4
+          fetch-depth: 0
+
+      - name: Setup PHP 8.2
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          coverage: none
+          tools: composer:v2
+
+      - name: Install dependencies (ignore platform reqs to allow downgrade tools)
+        run: composer install --no-interaction --prefer-dist --no-progress --ignore-platform-reqs
+
+      - name: Run Rector downgrade to PHP 7.4
+        run: ./vendor/bin/rector process --config rector/toPhp7.4.php
+
+      - name: Update composer.json PHP constraint to ">=7.4,<=8.0"
+        run: |
+          php -r '
+            $f = "composer.json";
+            $j = json_decode(file_get_contents($f), true, 512, JSON_THROW_ON_ERROR);
+            if (!isset($j["require"])) { $j["require"] = []; }
+            $j["require"]["php"] = ">=7.4,<=8.0";
+            file_put_contents($f, json_encode($j, JSON_PRETTY_PRINT|JSON_UNESCAPED_SLASHES) . "\n");
+          '
+
+      - name: Commit changes
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add -A
+          if ! git diff --cached --quiet; then
+            git commit -m "chore(downgrade): apply Rector PHP 7.4 and set composer PHP constraint"
+          else
+            echo "No changes to commit."
+          fi
+
+      - name: Compute new v1.x.y tag from release tag v2.x.y
+        id: tag
+        run: |
+          SRC_TAG="${{ github.event.release.tag_name }}"
+          # Convert v2.M.N -> v1.M.N
+          NEW_TAG="${SRC_TAG/v2./v1.}"
+          echo "new_tag=$NEW_TAG" >> "$GITHUB_OUTPUT"
+          echo "New tag: $NEW_TAG"
+
+      - name: Push branch and tag
+        env:
+          NEW_TAG: ${{ steps.tag.outputs.new_tag }}
+        run: |
+          git push origin php7.4
+          # Create or move tag to latest commit on php7.4
+          if git rev-parse "$NEW_TAG" >/dev/null 2>&1; then
+            git tag -d "$NEW_TAG"
+          fi
+          git tag "$NEW_TAG"
+          git push origin "$NEW_TAG"