feat: update macro DeriveRelatedEntity to deal with nested create mutation

[MedHeikelBouzayene]

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PR Info

• Closes https://github.com/SeaQL/seaography/issues/143

• Dependencies:
  • https://github.com/SeaQL/seaography/pull/187

• Dependents:
  • https://github.com/SeaQL/seaography/pull/187

New Features

• [x] Create an entity and its related entities in a single GraphQL query.

Changes

• [x] Add active_model to related_attr in sea-orm-macros.