Allow distinct types in `schema::custom()`

[sgoll]

PR Info

• Closes #2325

Bug Fixes

• [ ] Allow col and name to come from different DeriveIden structs in schema::custom().

Breaking Changes

• [ ] The signature of schema::custom() gains another generic type argument.

Strictly speaking, this may be considered a breaking change. However, it remains unclear whether explicitly stating the generic type argument is something that is actually done in the wild.

Rationale

The proposed change is in line with the existing signature of schema::enumeration(), another method that uses more than one IntoIden argument:

https://github.com/SeaQL/sea-orm/blob/aa0bbd9e017635ba646a76e7d7ac4f33bccd5db5/sea-orm-migration/src/schema.rs#L549-L560