fix: Python 3.9 compatibility

Author: azmeuk

scim2_models/base.py

@@ -429,7 +429,7 @@ def annotation_type_filter(item):
         return field_annotation
 
     @classmethod
-    def get_field_root_type(cls, attribute_name: str) -> type | None:
+    def get_field_root_type(cls, attribute_name: str) -> Optional[type]:
         """Extract the root type from a model field.
 
         For example, return 'GroupMember' for

scim2_models/rfc7643/schema.py

@@ -48,7 +48,7 @@ def make_python_model(
     obj: Union["Schema", "Attribute"],
     base: Optional[type[BaseModel]] = None,
     multiple=False,
-) -> "Resource" | "Extension":
+) -> Union[Resource, Extension]:
     """Build a Python model from a Schema or an Attribute object."""
     if isinstance(obj, Attribute):
         pydantic_attributes = {