Add support for delegated types

[Paul-Bob]

It'd be great if avo had support for delegated type fields. I think this could work like a belongs to association?

Originally posted by @iainbeeston in https://github.com/avo-hq/avo/discussions/1356#discussioncomment-5510587

There is a closed PR about this: https://github.com/avo-hq/avo/pull/2681