export and auto-commit docs/docs/api/openapi.json as part of test-api-contract workflow (#719)

- copies that openapi.json file to docs/docs/api/openapi.json as part of start-mock-server.sh.
- adds a step to the end of the test-api-contract workflow that just auto-commits changes to the docs/docs/api/openapi.json file.
- excludes docs/docs/api/openapi.json from pre-commit since its already been formatted by jq.

.github/workflows/test-api-contract.yaml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - main
+      - add-api-docs-workflow
     paths:
       - "oasst-shared/**"
       - "backend/**"
@@ -44,3 +45,9 @@ jobs:
         run: ./scripts/frontend-development/run-contract-test.sh
 
       - run: ./scripts/backend-development/stop-mock-server.sh
+
+      - uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          file_pattern: "docs/docs/api/openapi.json"
+          commit_message:
+            update docs/docs/api/openapi.json by run ${{ github.run_id }}