Add key-value metadata support for image upload (DATAMAN-156)

[digaobarbosa]

Description

Add support for passing key-value metadata during image upload via the Python SDK, matching the backend API capability.

Users can now attach custom metadata to images in a single request instead of uploading first then calling a separate API.

Implementation

• Added explicit metadata: Optional[Dict] parameter to upload(), single_upload(), upload_image(), and rfapi.upload_image()
• Local uploads: metadata serialized as JSON and added as a multipart form field
• Hosted uploads: metadata serialized as JSON and added as a query parameter
• Auto-detect hosted images (URLs) in project.upload() — no need for explicit hosted_image=True flag
• CLI support: -M/--metadata argument accepts JSON string

Type of change

• New feature

How has this change been tested?

• All 24 existing unit tests pass (test_rfapi.py + test_project.py)
• Added 2 new tests:
  • test_upload_image_local_with_metadata: verifies metadata in multipart body
  • test_upload_image_hosted_with_metadata: verifies metadata in query param
• Created demo scripts for manual testing:
  • tests/manual/demo_upload_local_metadata.py
  • tests/manual/demo_upload_hosted_metadata.py

Will the change affect Universe?

No

Docs

• Docs updated? N/A - internal API feature

Usage

project.upload("image.jpg", metadata={"camera_id": "cam001", "location": "warehouse"})

CLI:

roboflow upload image.jpg -p my-project -M '{"camera_id":"cam001"}'