Christian Schmidt

### Motivation / Background In #41717, `accepts_nested_attributes_for` got support for polymorphics associations created via `delegated_type`. I suggest this support is extended to polymorphic associations in general, not just those generated...

### Motivation / Background If you assign an invalid type to a belongs_to association, an `ActiveRecord::AssociationTypeMismatch` error is raised: ``` rails(dev)> d.user = 1 (rails):2:in '': User(#15408) expected, got 1...

Remove legacy code for old Rails and Ruby versions

2

Clean up legacy support code. - Bump Rails version requirement to 7.0. - Remove support code for old versions of Rails, Ruby and Mongoid. - Rails 7 requires Mongoid >=...