Make Slack message optional for manual dispatch

.github/workflows/nightly-v5-integtest.yml

@@ -6,6 +6,10 @@ on:
 
 
   workflow_dispatch:
+    inputs:
+      send-slack-message:
+        description: 'Send message to daq-release-notifications on failure?'
+        default: 'no'
 
 
 jobs:
@@ -105,7 +109,7 @@ jobs:
           /home/nfs/dunedaq/kill_stale_gunicorn_processes.sh
 
   send_slack_message:
-    if: failure()
+    if: failure() || (github.event_name == 'workflow_dispatch' && github.event.inputs.send-slack-message == 'yes')
     runs-on: daq
     name: send slack message
     needs: integration_tests