Add schema migrations

[Svedrin]

from #72 (comment)

To implement new features, we'll want to be able to do schema migrations. SQLAlchemy comes to mind, but maybe there are other options too.

[liquid-metal]

Unfortunately, I was unable to find a small tool/dependency for just database migrations. There are a few out there, but none of the ones I saw seemed to be maintained for a few years.

The maintained ones (I could find) seem to always come with an ORM (none of which I have used in the past):

• SQLAlchemy/alembic
• TortoiseORM/aerich
• SQLObject/sqlobject-admin
• django (which is much more obviously and is relatively large, unless it is possible to use the relevant parts as standalone package)

From the ORM side, there is also peewee (which I used in the past), though its migration mechanism is very bare-bones and explicitly meant for additional libraries to hook in, though again I could not find a maintained one. Also I found ponyorm, but that one has a 12y old open issue about a migration tool...

One more approach (that I am not a fan of) kept popping up: SQLite hast a user_version pragma that can serve as a basis for a home-made migration system. There are various posts describing this approach

Given that we find an option that seems to fit, I'd be willing to contribute for the adoption

[Svedrin]

I can imagine implementing an ORM is just something that comes with the territory. To be able to implement migrations, you'll need some kind of definition what the schema shall look like that you can introspect. Doing that in code is probably just the most useful thing to do.

From the ones on the list, the only one I'm actually familiar with (and that I know I'll enjoy) is Django. From my PoV, it would be fine to just go with Django, even though it does bring a lot more to the table than we currently think we need. But it'd be a very future-proof option.

I think I'd like to take a stab at SQLAlchemy as well though, just for comparison. But if we combine Flask, Jinja2 and SQLAlchemy, I'm getting a bit of a vibe like we're building an accidental copy of Django, so it might just be better to go with the real thing 😅

[liquid-metal]

Alright, I will give Django a shot and compare with SQLAlchemy. I will file a draft PR shortly to make the progress visible