Extract remaining DB models to the common crate

[wojcik91]

Put remaining DB models into the common crate.

This should enable us to finally split all components (gRPC server, bidi server, API etc) into separate crates.

[wojcik91]

Done in #1713

What remains are models related to webhooks, activity log and enrollment, but the heaviest stuff is done.
We should be able to pull out more components from core.