ci: Add config file for CodeRabbit with custom rules

[spetrosi]

Sourcery that we currently use cannot read documentation files and best
practices, it's rather a refactoring tool.
So I want to introduce CodeRabbit that allows creating .coderabbit.yaml with
custom rules and conventions.

Signed-off-by: Sergei Petrosian spetrosi@redhat.com

Summary by Sourcery

Add a CodeRabbit configuration file to enforce repository-specific PR conventions and review guidelines.

CI:

• Configure CodeRabbit review settings, disabling nonessential features and enabling checks for PR title and description format.

Documentation:

• Document role- and repository-specific conventions for tasks, handlers, tests, templates, variables, Python code, and README updates via CodeRabbit path instructions.

Chores:

• Centralize project best practices and coding conventions in a managed .coderabbit.yaml file synced from the shared .github repository.

[sourcery-ai]

Reviewer's Guide

Adds a project-wide CodeRabbit configuration file to enforce PR formatting and Ansible/linux-system-roles conventions during automated code review, while disabling most non-essential CodeRabbit features.

File-Level Changes

Change	Details	Files
Introduce CodeRabbit configuration file with organization-wide review rules and path-specific Ansible conventions.	Create .coderabbit.yaml to configure CodeRabbit behavior for this repository, disabling fun/auto features and enabling pre-merge checks for PR titles and descriptions. Define custom instructions for reviewing Ansible tasks, handlers, tests, templates, defaults/vars, and Python code, including no_log usage, OSTree-safe package installation, idempotency, check-mode expectations, and test coverage requirements. Require documentation updates in README.md for new user-facing variables and specify conventions for variable naming and template headers.	.coderabbit.yaml

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[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path=".coderabbit.yaml" line_range="202-205" />
<code_context>
+    - path: "defaults/**/*.yml"
+      instructions: |
+        - All variables MUST be prefixed with `keylime_server_`
+        - All variables MUST be stored in the file defaults/main.yml, Ansible
+          doesn't include variables from other files.
+        - These are user-facing API variables
+        - For every new variable introduced in this file, verify that it is
</code_context>
<issue_to_address>
**suggestion:** Wording about Ansible defaults loading behavior is misleading and may confuse contributors.

"Ansible doesn't include variables from other files" is inaccurate: Ansible loads all files under `defaults/` as role defaults. If this is a project convention (using only `defaults/main.yml`), please phrase it as a policy rather than a tool limitation, e.g., "All variables MUST be stored in `defaults/main.yml`; other files under `defaults/` MUST NOT be used in this role."

```suggestion
        - All variables MUST be prefixed with `keylime_server_`
        - All variables MUST be stored in `defaults/main.yml`; other files under
          `defaults/` MUST NOT be used for variable definitions in this role.
        - These are user-facing API variables
```
</issue_to_address>

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[sourcery-ai]

suggestion: Wording about Ansible defaults loading behavior is misleading and may confuse contributors.

"Ansible doesn't include variables from other files" is inaccurate: Ansible loads all files under defaults/ as role defaults. If this is a project convention (using only defaults/main.yml), please phrase it as a policy rather than a tool limitation, e.g., "All variables MUST be stored in defaults/main.yml; other files under defaults/ MUST NOT be used in this role."

Suggested change

	- All variables MUST be prefixed with `keylime_server_`
	- All variables MUST be stored in the file defaults/main.yml, Ansible
	doesn't include variables from other files.
	- These are user-facing API variables
	- All variables MUST be prefixed with `keylime_server_`
	- All variables MUST be stored in `defaults/main.yml`; other files under
	`defaults/` MUST NOT be used for variable definitions in this role.
	- These are user-facing API variables