# What this PR does
This PR simplifies code of maintenance mode.
1. Perform distribution/escalation maintenance checks in send_signal...
tasks.
2. Use usual alert distribution flow for the maintenance incident.
3. Decouple maintenance mode from slack (all, except
**notify_about_maintenance_action** methods, I don't want to make this
PR too big)
As a bonus from these changes, maintenance mode now mute alert group
delivery in all chatops integrations, not only in slack. (Before,
incidents happened while maintenance were posted to telegram and msteams
anyway)
## Checklist
- [ ] Tests updated
- [ ] Documentation added
- [ ] `CHANGELOG.md` updated
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