`File.file_name` marked as `Optional` but is required when used in `multipart/form-data`

Describe the bug

In types.py:

https://github.com/openapi-generators/openapi-python-client/blob/0399271be4eb012f83ac3023939ff48e364634e9/openapi_python_client/templates/types.py.jinja#L24

file_name is marked Optional, so it seems like the user could omit it. But if they do to a multipart/form endpoint, backends such as DjangoRestFramework will return:

Status Code: 400 (Bad Request)
Content    : {"file":["The submitted data was not a file. Check the encoding type on the form."]}

This means that users will not get a type checking error if they forget to include a file_name in this scenario.

It seems like perhaps a MultipartFile type is needed to be used to correctly model this?

@define
class MultipartFile:
    """Contains information for multipart file uploads"""

    payload: BinaryIO
    file_name: str
    mime_type: Optional[str] = None

    ...

OpenAPI Spec File

  /upload/:
    post:
      operationId: upload
      requestBody:
        content:
          multipart/form-data:
            schema:
              $ref: '#/components/schemas/UploadRequest'
        required: true

components:
  schemas:
    UploadRequest:
      type: object
      properties:
        file:
          type: string
          format: binary
      required:
      - file

Desktop (please complete the following information):

• OS: macOS 13.6.4
• Python Version: 3.12.0
• openapi-python-client version: 0.16.1

Additional context

The generated Swagger UI page for this endpoint looks like:

Backend versions:

• Django 4.2.11
• djangorestframework 3.14.0
• drf-spectacular 0.27.1

Bắt đầu từ định nghĩa được liên kết trong templates/types.py.jinja và theo dõi cách các trường tệp multipart/form-data được biểu diễn trong các client được tạo. Tái hiện đặc tả UploadRequest được cung cấp, sau đó xác minh rằng một tệp multipart bắt buộc cũng yêu cầu file_name trong kiểu được tạo và tránh được lỗi backend đã báo cáo.