Feature: always migration(s)

[mfridman]

In many systems, it's quite common to have migration(s) that insert some piece of data that should always be there. For example, reference tables or a server admin user.

However, when you squash migrations you need to remember those bespoke migrations and include them in the squashed migration file.

The alternative solution is to build some tooling that does this at application startup.

I wonder if there's an elegant solution here for goose to manage these sort of "data migrations" outside the normal migration versioning flow.

Related:

• Support repetable migration #108
• Ability to add repeatable SQL migrations #472