Multipart form request does not set headers for file and JSON data parts

[Ayeshas09]

Is this a new bug?

• I believe this is a new bug
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

When sending multipart form requests, the SDK does not attach the headers such as Content-Type to individual parts.

Expected Behavior

Each part of the multipart request should include its appropriate headers.

Steps To Reproduce

1. Create a multipart request containing both a file and a JSON parameter.
2. Observe the request being sent using a request inspector (e.g., Beeceptor or Postman).
3. Notice that headers such as Content-Type: application/json for JSON data are missing.

Environment

- **OS**: Windows
- **Node.js Version**: node v22.15.1
- **TypeScript Version**:
- **Package Manager & Version**:
- **Compiler / Runtime Details**:
- **Framework / Library Versions (if applicable)**:
- **Browser Version (if applicable)**:
- **SDK Name**:

Relevant log output

Additional Context

No response