Updates the ApiClient to allow uploading of pdf files for the host messaging upload endpoint by:
"implementing" serializeToString for multipart/form-data values. Since this method is used for http signature authorization, which Telnyx doesn't support at the moment, the "implementation" simply serializes the form params (essentially just the filenames) of any multipart/form-data
changing the multipart/form-data serialization logic, which IS used to serialize files to send to the server, to only support pdf files. The only endpoint with upload functionality that the sdk currently supports is the hosted messaging endpoint, which must be a pdf. This is validated server-side by checking the content-type. This is a temporary workaround until more upload endpoints are supported
Updates the ApiClient to allow uploading of pdf files for the host messaging upload endpoint by: