Accepts a multipart/form-data request only — this endpoint does not accept application/json.

Array binding convention

Documents is bound from form-data as a list, so each item's fields must use an
indexed key format: Documents[i].PropertyName (zero-based index). A plain
Documents key without an index will not bind.
Example — uploading two documents for one loan:

Field notes

• LoanId — internal GUID of the loan the documents belong to.
• Documents[i].File — binary content of the file for item i.
• Documents[i].DocumentTypeId — GUID identifying the document type. Must be a valid ID for the caller's
  workspace — call
  GET /api/v1/core/resources/get-upload-document-types-by-workspace first to retrieve the allowed document type IDs
  for the current workspace.
  Passing an arbitrary or cross-workspace GUID will be rejected.
• Documents[i].DocumentName — display name shown to users; does not need to match the uploaded filename.

Common mistakes

• Sending Documents as a JSON string/array instead of individual indexed form fields.
• Manually setting a Content-Type: multipart/form-data header without a boundary — let your HTTP client generate
  it.
• Omitting the index (e.g. Documents.File instead of Documents[0].File) — the model binder can't map this to a
  list item.
• Hardcoding or reusing a DocumentTypeId from another workspace/environment instead of fetching it from
  get-upload-document-types-by-workspace.