Add OpenTelemetry VCS attributes (#32904)

.github/workflows/build-container-image.yml

@@ -92,6 +92,7 @@ jobs:
           build-args: |
             MASTODON_VERSION_PRERELEASE=${{ inputs.version_prerelease }}
             MASTODON_VERSION_METADATA=${{ inputs.version_metadata }}
+            SOURCE_COMMIT=${{ github.sha }}
           platforms: ${{ inputs.platforms }}
           provenance: false
           builder: ${{ steps.buildx.outputs.name || steps.buildx-native.outputs.name }}