Cleanup and add test for the database

[TimoPtr]

Summary

Move the migration into a dedicated file to make it easier to see the database configuration. Add instrumentation test for the migration, for now it only tests migration from 24 to latest. Later we should add individual tests for migrations to verify the behavior.

Checklist

• New or updated tests have been added to cover the changes following the testing guidelines.
• The code follows the project's code style and best_practices.
• The changes have been thoroughly tested, and edge cases have been considered.
• Changes are backward compatible whenever feasible. Any breaking changes are documented in the changelog for users and/or in the code for developers depending on the relevance.

[jpelgrom]

To be honest I'm not convinced this is all a cleanup, everything you moved was already at the end of the file. The automated test is nice though.

[TimoPtr]

To be honest I'm not convinced this is all a cleanup, everything you moved was already at the end of the file. The automated test is nice though.

Well I wanted to have only the database definition in the file to make it cleared. Migration is something else IMO, I hesitated to create a file for each migration, but I decided that for now it's fine like this.

For large migration or complex one I would like one file and one associated test for instance.