Healthchecks

Improvements

• Implement Pushover emergency alert cancellation when check goes up
• Add “The following checks are also down” section in Telegram notifications
• Add “The following checks are also down” section in Signal notifications
• Upgrade to django-compressor 3.0
• Add support for Telegram channels (#592)
• Implement Telegram group to supergroup migration (#132)
• Update the Slack integration to not retry when Slack returns 404
• Refactor transport classes to raise exceptions on delivery problems
• Add Channel.disabled field, for disabling integrations on permanent errors
• Upgrade to Django 4
• Bump the min. Python version from 3.6 to 3.8 (as required by Django 4)

Bug Fixes

• Fix report templates to not show the “started” status (show UP or DOWN instead)
• Update Dockerfile to avoid running “pip wheel” more than once (#594)