ci: fix test failure Slack notifications (#19766)

- Skip notifications for cancelled workflows. Cancellation can be
manual or caused by branch concurrency limits.
- Fix multi-line JSON parsing error by only printing the summary line
of the commit message. We do not need more than this in Slack.
- Update Slack webhook name to match purpose.

.github/workflows/go-tests.yml

@@ -499,19 +499,33 @@ jobs:
       - name: evaluate upstream job results
         run: |
           # exit 1 if failure or cancelled result for any upstream job
+          # this ensures that we fail the PR check regardless of cancellation, rather than skip-passing it
+          # see https://docs.github.com/en/actions/using-jobs/using-conditions-to-control-job-execution#overview
           if printf '${{ toJSON(needs) }}' | grep -E -i '\"result\": \"(failure|cancelled)\"'; then
             printf "Tests failed or workflow cancelled:\n\n${{ toJSON(needs) }}"
             exit 1
           fi
+      - name: Set failure Slack commit message summary
+        # failure() ensures this runs even if the test eval step exits 1
+        if: failure()
+        run: |
+          # if failure (not cancelled), notify Slack
+          if printf '${{ toJSON(needs) }}' | grep -E -i '\"result\": \"(failure)\"'; then
+            printf "Tests failed, notifying Slack"
+            echo "FAILED_TESTS=true" >> $GITHUB_ENV
+            echo "COMMIT_MESSAGE_SUMMARY=$(echo ${{ github.event.head_commit.message }} | head -n 1)" >> $GITHUB_ENV
+          fi
       - name: Notify Slack
-        if: ${{ failure() && (github.ref_name == 'main' || startsWith(github.ref_name, 'release/')) }}
+        # failure() ensures this runs even if the test eval step exits 1
+        # FAILED_TESTS must also be checked to avoid running this step on cancellation due to the summary check above
+        if: ${{ failure() && env.FAILED_TESTS == 'true' && (github.ref_name == 'main' || startsWith(github.ref_name, 'release/')) }}
         id: slack
         uses: slackapi/slack-github-action@e28cf165c92ffef168d23c5c9000cffc8a25e117 # v1.24.0
         with:
           # github.event.head_commit.message and github.ref_name both rely on this event occurring on a push / merge
           payload: |
             {
-              "message": "❌ ${{ github.workflow }} workflow failed: \n\n- Run: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} \n- Branch: ${{ github.ref_name }} \n- Message: ${{ github.event.head_commit.message }} \n- Author: ${{ github.event.sender.login }}"
+              "message": "❌ ${{ github.workflow }} workflow failed: \n\n- Run: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }} \n- Branch: ${{ github.ref_name }} \n- Message: ${{ env.COMMIT_MESSAGE_SUMMARY }} \n- Author: ${{ github.event.sender.login }}"
             }
         env:
-          SLACK_WEBHOOK_URL: ${{ secrets.CONSUL_NIGHTLY_INTEG_TEST_SLACK_WEBHOOK }}
+          SLACK_WEBHOOK_URL: ${{ secrets.CONSUL_PROTECTED_BRANCH_TEST_SLACK_WEBHOOK }}