Requests::request_multiple() does not honor $auth option

[alpipego]

If individual requests have an option for $auth, the authentication CURLOPTs don't get set as curl.before_send is never dispatched.

Manually setting an 'Authorization' header overcomes this limitation. I suspect this is not intended behaviour however, cf. documentation in #48349.

[dd32]

​Requests is an external project, and this should be reported directly to the projects ​Github project.