Make Slack notifications louder for deploy issues

[janbrasna]

Description

If a failure is posted to #www-notify from GHA workflows here, all what's different from success or info is the color of the bar. Given the amount of events notified, not sure how "loud" folks have settings for the channel.

Would it help if the failure conditionally included some more verbose content, like @here to ping folks who happen to be around drawing more attention to the fact there is an issue right away?

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Success Criteria

• Investigate if just plain @mention text turns into interactive rich content when posted via the slack action
• Consider the utility of a failure message to draw attention to itself
• It can only be included for stage or tag triggers for some tests, but include main/dev failures in build+deploy failures as needed

┆Issue is synchronized with this Jira Task
┆Priority: P2
┆Sprint: Backlog