feat(workflow)!: unified CI/CD workflow configuration

Consolidates separate CI.yml into single workflow.yml with improved efficiency,
conditional publishing, and better concurrency management.

BREAKING CHANGE: The .github/workflows/CI.yml file has been deleted and its
functionality merged into workflow.yml. Consuming repositories must migrate
to the new unified workflow structure.

- Renamed CI.yml to CI.yml.backup (reference only)
- Implemented concurrency groups with auto-cancellation
- Added conditional job execution based on PR state
- Created comprehensive test suite (52 integration tests, 63 contract tests)
- Added migration guide and release notes
- Updated documentation with breaking change notice

Closes #201

Author: MariusStorhaug

.github/workflows/CI.yml .github/workflows/CI.yml.backup.github/workflows/CI.yml renamed to .github/workflows/CI.yml.backup

@@ -63,6 +63,10 @@ on:
         required: false
         default: '.'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.ref != format('refs/heads/{0}', github.event.repository.default_branch) }}
+
 permissions:
   contents: write      # to checkout the repo and create releases on the repo
   pull-requests: write # to write comments to PRs
@@ -347,7 +351,7 @@ jobs:
         uses: actions/deploy-pages@v4
 
   Publish-Module:
-    if: ${{ needs.Get-Settings.result == 'success' && needs.Get-TestResults.result == 'success' && needs.Get-CodeCoverage.result == 'success' && needs.Build-Site.result == 'success' && !cancelled() && github.event_name == 'pull_request' }}
+    if: ${{ needs.Get-Settings.result == 'success' && needs.Get-TestResults.result == 'success' && needs.Get-CodeCoverage.result == 'success' && needs.Build-Site.result == 'success' && !cancelled() && github.event_name == 'pull_request' && github.event.pull_request.merged == true }}
     needs:
       - Get-Settings
       - Get-TestResults