add concurrency to ci (#8271)

* add concurrency to ci

* add readme for workflows

.github/workflows/test-db-changes.yml

@@ -12,14 +12,19 @@ on:
       - '.github/workflows/test-schema-changes.yml'
   workflow_dispatch: # Manual
 
-permissions:
-  contents: read
+# This allows a subsequently queued workflow run to interrupt previous runs
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id}}
+  cancel-in-progress: true
 
 defaults:
   run:
     # fail-fast using bash -eo pipefail. See https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#exit-codes-and-error-action-preference
     shell: bash
 
+permissions:
+  contents: read
+
 jobs:
   test-db-changes:
     runs-on: ubuntu-latest