Add new workflow to ping Slack every time a certain team is assigned as PR reviewer or tagged in a PR comment. (#41067)

* Add new workflow to ping Slack every time a certain team is assigned as PR reviewer or tagged in a PR comment.

* Fix workflow after getting feedback from review.

* Fix test-assistant-pr-review workflow so that it also triggers on PR review comments.

* Remove the pull_request trigger from test-assistant-pr-review.yml as it was added only to improve testability.

.github/workflows/test-assistant-pr-review.yml

@@ -0,0 +1,48 @@
+name: Send PRs that require review to Slack
+
+on:
+  pull_request_target:
+    types: [review_requested]
+  issue_comment:
+    types: [created]
+  pull_request_review_comment:
+    types: [created]
+
+permissions: {}
+
+jobs:
+  send-pr-to-slack-for-review:
+    runs-on: ubuntu-20.04
+    env: 
+      WOO_PR_TESTING_REVIEW_TEAM: ${{ secrets.WOO_PR_TESTING_REVIEW_TEAM }}
+    steps:
+      - name: Send ping to Slack for a new review
+        uses: archive/github-actions-slack@d9dae40827adf93bddf939db6552d1e392259d7d
+        id: notify-review
+        if: |
+          (github.event_name == 'pull_request' || github.event_name == 'pull_request_target') &&
+          github.event.action == 'review_requested' &&
+          github.event.requested_team.slug == env.WOO_PR_TESTING_REVIEW_TEAM
+        with:
+          slack-bot-user-oauth-access-token: ${{ secrets.TEST_ASSISTANCE_BOT_TOKEN }}
+          slack-channel: ${{ secrets.WOO_PR_TESTING_REVIEW_SLACK_CHANNEL }}
+          slack-text: |
+              <!subteam^${{ secrets.WOO_PR_TESTING_REVIEW_TEAM_ID }}> was asked to review this PR:
+              <${{ github.event.pull_request.html_url }}|${{ github.event.pull_request.title }}> :thread:
+          slack-optional-unfurl_links: false
+          slack-optional-unfurl_media: false
+          
+      - name: Send ping to Slack about a new comment
+        uses: archive/github-actions-slack@d9dae40827adf93bddf939db6552d1e392259d7d
+        id: notify-comment
+        if: |
+          (github.event_name == 'issue_comment' || github.event_name == 'pull_request_review_comment') &&
+          contains(github.event.comment.body, env.WOO_PR_TESTING_REVIEW_TEAM)
+        with:
+          slack-bot-user-oauth-access-token: ${{ secrets.TEST_ASSISTANCE_BOT_TOKEN }}
+          slack-channel: ${{ secrets.WOO_PR_TESTING_REVIEW_SLACK_CHANNEL }}
+          slack-text: |
+              <!subteam^${{ secrets.WOO_PR_TESTING_REVIEW_TEAM_ID }}> was mentioned in a comment:
+              <${{ github.event.comment.html_url }}|${{ github.event.issue.title }}> :speech_balloon:
+          slack-optional-unfurl_links: false
+          slack-optional-unfurl_media: false