Update Slack configuration in GitHub Actions (for slack-github-actions v2.0.0) (#1004)

It turns out a lot more changed in slack-github-actions v2.0.0 than
their changelog suggested (update to v2.0.0 in this PR: #1002).

Therefore change the configuration to fit the new expected syntax (see
https://github.com/slackapi/slack-github-action/releases/tag/v2.0.0)
Hopefully it now works fully correctly!

Co-authored-by: Krzysztof Kiewicz <[email protected]>

Author: avelanarius

.github/workflows/integration-tests.yml

@@ -74,23 +74,21 @@ jobs:
         if: ${{ failure() && github.event_name == 'push' && github.ref == 'refs/heads/main' }}
         uses: slackapi/[email protected]
         with:
-          channel-id: ${{ secrets.SLACK_CHANNEL_ID }}
-          slack-message: |
-            :exclamation: *Integration tests failed.* :exclamation: <!channel>
-            *Last commit by:* ${{ steps.get_author.outputs.author }}
-            *Workflow run URL:* ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
-        env:
-          SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
+          method: chat.postMessage
+          token: ${{ secrets.SLACK_BOT_TOKEN }}
+          payload: |
+            channel: ${{ secrets.SLACK_CHANNEL_ID }}
+            text: ":exclamation: *Integration tests failed.* :exclamation: <@channel>\n*Last commit by:* ${{ steps.get_author.outputs.author }}\n*Workflow run URL:* ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
 
       - name: Send Slack notification on success
         if: ${{ success() && github.event_name == 'push' && github.ref == 'refs/heads/main' }}
         uses: slackapi/[email protected]
         with:
-          channel-id: ${{ secrets.SLACK_CHANNEL_ID }}
-          slack-message: |
-            :white_check_mark: *Integration tests passed.* Good job team!
-            *Last commit by:* ${{ steps.get_author.outputs.author }}
-            *Workflow run URL:* ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+          method: chat.postMessage
+          token: ${{ secrets.SLACK_BOT_TOKEN }}
+          payload: |
+            channel: ${{ secrets.SLACK_CHANNEL_ID }}
+            text: ":white_check_mark: *Integration tests passed.* Good job team!\n*Last commit by:* ${{ steps.get_author.outputs.author }}\n*Workflow run URL:* ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}"
         env:
           SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}