Migrate lastlogin column from int32 to bigint

[ljacqu]

As mentioned by @FabioZumbi12 we switched to milliseconds timestamp from seconds timestamp at some point.

• Implement a migration of the datasource when necessary
• Check when we changed to millis
• Verify that we now really use milliseconds everywhere

[ljacqu]

This took longer than expected because I struggled with H2. Looks like an integration test for the migrations isn't going to happen... 🌵
I had a quick look at the codebase and didn't see int used for lastlogin throughout the history. This is still critical enough that it warrants a migration to be implemented.
I'll take a second look tomorrow before closing this issue.

[ljacqu]

Closing without adding migration for SQLite; seems like there it's always been a bigint. Please open a new issue if someone does have a lastlogin column in SQLite that needs migrating.