Fix remote_fields Definition in Pydantic Models to Make Field Optional and Nullable

[BPLint]

This PR corrects the field definition of "remote_fields" in the Pydantic models, which was causing validation errors. Previously, the omission of = None at the end of the field definition inadvertently made the field required, despite it being nullable. Since the remote_fields field is not present in every API response and should be both optional and nullable, this update properly adjusts its definition.

Changes:

• Updated the remote_fields field in the Pydantic models to include = None, ensuring it is treated as an optional field that can be None when not present in the API response.

Context:
This change resolves validation errors encountered during the parsing of API responses where remote_fields was missing, and the Pydantic models incorrectly treated it as a required field.

Testing:

• Verified that the models now properly handle cases where remote_fields is omitted or returns an empty array.
• Confirmed that responses with or without this field pass validation without errors.

Reference:
https://docs.pydantic.dev/latest/migration/#required-optional-and-nullable-fields
Field definition F4 (required, nullable) is correct here.
See also:
#98