Display full event list for Trigger Once Alerts

[dabbabi-zayani]

The App notification displays a list of events when configured with Trigger "For each result". However for trigger "Once" , only the first event is displayed . It would be good , if the full list of events is displayed for Trigger "Once" alerts as well.

The line in the code corresponding to retrieving the first event should be this one : https://github.com/splunk/slack-alerts/blob/main/src/app/bin/slack.py#L37

Thank you.