Github action for auto-assigning reviewers (#35846)

* First draft of github action on PR opening for auto-assigning reviewers

* fix missing import

* Don't reassign reviewers if we already have them

* Temporarily comment out the opened line so we can test the script

* Correct path for codeowners file

* Update workflow permissions

* Update workflow permissions

* Update debug logs

* Strip inline comments

* Remove prefix

* Request reviews instead of assigning

* Request reviews instead of assigning

* Add TODO

* Use pull-request-target instead

* Update the script

* Set back to pull_request for testing

* Set to pull_request_target, testing works!

* Add licence

* Tighten up one of the globs

* Refactor things to be a bit less convoluted

* Only assign reviewers when marked ready for review

.github/workflows/assign-reviewers.yml

@@ -0,0 +1,26 @@
+name: Assign PR Reviewers
+on:
+  pull_request_target:
+    branches:
+      - main
+    types: [ready_for_review]
+
+jobs:
+  assign_reviewers:
+    permissions:
+       pull-requests: write
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.13'
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install PyGithub
+      - name: Run assignment script
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: python .github/scripts/assign_reviewers.py