Fix KeyError @ fields to JSON:API schema rendering

As the field called id according to rules guided
by JSON:API is required it's processing must be
be excluded in iteration's control structure
used to apply requirment state to fields being
either child of property called attributes or
relationships.

Author: alida

starlette_jsonapi/openapi.py

@@ -106,7 +106,7 @@ def fields2jsonschema(self, fields, *, ordered=False, partial=None):
                 properties['attributes']['properties'][observed_field_name] = prop
             # TODO: support meta fields
 
-            if field_obj.required:
+            if field_obj.required and field_name != 'id':
                 if not partial or (
                     is_collection(partial) and field_name not in partial
                 ):