Tests: add test cases for migrations

[hirotasoshu]

We currently have no tests to ensure that migrations are backwards and forwards compatible. My proposal is to add this tests using django-test-migrations and include them to our CI pipeline. We could also add a linter for migrations

Additional context
Originally discussed in #1191

[aleksihakli]

Sounds like a good proposal. Fix for issue #1191 has been merged and released but it would be great to have backwards-compatibility available in the future for all releases, where possible.