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 response_process().
List. Holds the components for an HTTP request, presumably created
with request_develop() or request_build(). Must contain a method and
url. If present, body and token are used.
...
Optional arguments passed through to the HTTP method.
user_agent
A user agent string, prepared by httr::user_agent(). When
in doubt, a client package should have an internal function that extends
gargle_user_agent() by prepending its return value with the client
package's name and version.