Consider seeding database before testing migration paths

Description

We do test migrations paths in CI which is great. One problem with this approach is that we are not seeding the database (seed_fu is mostly empty in test environment) because it takes a significant amount of time.

However we could benefit from having a dummy database and some fixtures in the database, because it can help to catch more problems with migrations.

The prerequisite is that this seeding mechanism should be fast!

/cc @bjgopinath