Ingest files into Uploadcare both via direct client upload and by fetching from a remote URL, then manage the resulting files through the REST API

Steps

1. For direct uploads, POST file data to the Upload API (or use Uploadcare's widget/SDK) to receive a file UUID once the upload completes
2. For remote ingestion, POST the source URL to the `/from_url/` Upload API endpoint, which returns a `token` for tracking the async fetch rather than the file UUID itself
3. Poll the `/from_url/status/` endpoint with that token until the fetch completes, at which point the response includes the actual file UUID to use going forward
4. Pass `save_URL_duplicates`/`check_URL_duplicates` parameters on `/from_url/` calls if you want Uploadcare to deduplicate repeated fetches of the same source URL instead of creating a new file each time
5. Use the REST API (base `https://api.uploadcare.com/`, all paths ending in `/`) to manage the resulting files afterward — read metadata, organize into groups, or delete files as needed