Refactor Add_documents API

[wanliAlex]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  we move the query parameters non_tensor_fields, use_existing_tensors, image_download_headers, model_auth, mappings to the request body.

• What is the current behavior? (You can also link to an open issue here)
  non_tensor_fields, use_existing_tensors, image_download_headers, model_auth, mappings are query parameters

• What is the new behavior (if this is a feature change)?
  they are now moved to the query body as nonTensorFields, useExistingTensors, imageDownloadHeaders, modelAuth, mappings

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  yes.
  for py-marqo users, they need to upgrade the py-marqo version
  for bash curl users, they need to change their requests

marqo will still support old APIs recently but my remove them in the near future.

• Have unit tests been run against this PR? (Has there also been any additional testing?)
  running

• Related Python client changes (link commit/PR here)
  working on

• Related documentation changes (link commit/PR here)
  finished

• Other information:

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added / updated (for bug fixes / features)

[farshidz]

As discussed I suggest avoiding old and new in names so that we can easily remove the deprecated API in the future