Postgres domain types

[Huliiiiii]

Discussed in #2862

^{Originally posted by sfried December 19, 2025}
In postgres, domains provide a very convenient means of defining a new type, with its own enforcement mechanisms and documentation clarity. A bijection should be created between these two:

• sea-orm-cli's generate entity should create the relevant newtypes, and use those types in the generated models
• sea-orm should recognize newtypes being used in a model, and create the relevant domains (even if the new domain doesn't have the full checking defined in the rust code)