# What this PR does
This PR adds
[django-migration-linter](https://github.com/3YOURMIND/django-migration-linter)
to keep database migrations
backwards compatible
- we can automatically run migrations and they are zero-downtime, e.g.
old code can work with the migrated database
- we can run and rollback migrations without worrying about data safety
- OnCall is deployed to the multiple environments core team is not able
to control
See [django-migration-linter
checklist](https://github.com/3YOURMIND/django-migration-linter/blob/main/docs/incompatibilities.md)
for the common mistakes and best practices
## Which issue(s) this PR fixes
## Checklist
- [ ] Tests updated
- [ ] Documentation added
- [ ] `CHANGELOG.md` updated
---------
Co-authored-by: Joey Orlando <joey.orlando@grafana.com>
* move mobile notifications to a separate backend, remove critical notification
* remove outdated mobile app code
* MOBILE_APP_PUSH_NOTIFICATIONS_ENABLED -> FEATURE_MOBILE_APP_INTEGRATION_ENABLED
* create error log if no devices are set up
* move mobile auth related code to the mobile_app Django app
* move mobile auth related code to the mobile_app Django app
* move mobile auth related code to the mobile_app Django app
* fix typing
* add GCMDevice todos
* add user connection capabilities
* add user connect/disconnect to the messaging backend
* move APNS endpoint to mobile_app Django app
* restore critical notifications
* support hackathon app
* tweak migrations so mobile app auth tokens are preserved
* reuse notify_by IDs
* use mobile app template to render push notification
* add GCM/FCM (Android) support
* fix unlink user
* logger.error -> logger.info
