Allow db_url parameter to create_database_migration_numbered_style

[RudolfCardinal]

Part of fixing the missing-migration-check.yml problem in ucam-department-of-psychiatry/camcops#388

[RudolfCardinal]

If you're happy, I'll (a) merge this and push to PyPI, (b) complete the changes to ucam-department-of-psychiatry/camcops#388 with a proper cardinal_pythonlib version number.

[martinburchell]

Unfortunately we've duplicated some effort here but it might that we can combine our efforts.

master...throw-exception-if-migration-fails is perhaps a little less ugly. I infer from sqlalchemy/alembic#1089 that it is OK to call the command API directly, though specifying the autogenerate flag again in the additional cmd_opts does seem a bit suboptimal.

How about we adopt my solution but keep your other cosmetic changes (though the release date in the changelog appears to have gone back in time). If we wanted to stick to calling alembic through subprocess.call() we'd need to change that to subprocess.run() with check=True otherwise any error from alembic gets hidden.

[RudolfCardinal]

Yours is much nicer. Yes, if we can use the API directly that is far preferable, and allows a much better db_url tweak.