Upload Supporting Document

Uploads a supporting document for a provider by ID. This endpoint accepts a multipart/form-data request with a file and metadata.

- The uploaded document is associated with the provider and saved in the system.
- Only valid files and supported document metadata will be processed.
- Returns a confirmation once the document is uploaded successfully.

Authorization:
- Requires an Bearer access token.

Possible Errors:
- `400 Bad Request`: If the file or metadata is invalid.
- `404 Not Found`: If the provider with the given ID does not exist.