Build multipart form data elements. The form_file function uploads a
file. The form_data function allows for posting a string or raw vector
with a custom content-type.
form_file(path, type = NULL) form_data(value, type = NULL)
| path | a string with a path to an existing file on disk |
|---|---|
| type | MIME content-type of the file. |
| value | a character or raw vector to post |