Multiple Ways to Define Foreign Keys

Foreign keys can be defined in 2 ways:

1. Using the __foreign_keys__ special section (recommended):

   __foreign_keys__:
     user_id: [User, id]
   user_id: foreign_key
   

2. Using the field definition with references:

   user_id:
     type: foreign_key
     references:
       schema: User
       field: id