Changes to Create custom field definition

added the optional property code to the response with the 400 status

added the optional property code to the response with the 401 status

added the optional property code to the response with the 403 status

added the optional property code to the response with the 409 status

added the optional property code to the response with the 500 status

added the new Extension enum value to the schema/oneOf[subschema #10: CustomFieldResourceReferenceSchema]/allowed_types/items response property for the response status 201

added the new Extension enum value to the scope_type response property for the response status 201

added the new Extension enum value to the target_type response property for the response status 201

added the new Extension enum value to the request property schema/oneOf[subschema #10: CustomFieldResourceReferenceSchema]/allowed_types/items

added the new Extension enum value to the request property scope_type

added the new Extension enum value to the request property target_type

endpoint added