Feat: Test migrations and seeders in GitHub CI

[rinkp]

Description

This pull request introduces a simple check for migrations and seeders. Whenever seeders/migrations have been changed, it does the following checks:

• Migrate base branch
• Seed base branch
• Test forward migration to head branch
• Seed using seeders of head branch
• Rollback migrations to base branch migrations

Related issues/external references

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• [] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation improvement (no changes to code)
• Other: CI change

[rinkp]

This is expected to fail now (because GH-516 needs to be merged to repair building AND because the docker-compose.github.yml file is not yet present on the base branch). See https://github.com/GEWIS/gewisdb/actions/runs/21805157073 for an example of a succesful run.

[tomudding]

Awesome work!