pass basic auth credentials in http proxy config

[nosovk]

Time to time we have some services that does not support built-in authorization, and in common case we would like to put them behind warpgate.
In common case we protect services like that by adding basic auth on top of them at nginx or traefik level.

It would be nice pass authorization headers in requests from warpgate to http target,

In that case, we can manage access to http target without revealing basic auth password.