Intended primarily for internal use in client packages that provide
high-level wrappers for users.
request_make() does very little: calls an
HTTP method, only adding a user agent. Typically the input is created with
request_build() and the output is processed with
request_make(x, ..., user_agent = gargle_user_agent())
Optional arguments passed through to the HTTP method.
A user agent string, prepared by
Object of class
response from httr.