Pass authorization header with oauth token remapped on the backend

Overriding the authentication header may override some flow the user has on the backend, we need a way to pass this as some other special header like X-IBM-OAuth-Header or something

No files, tests, or entry points are identified in the issue. Start by tracing the backend authentication-header remapping flow and determine how a separate OAuth header should coexist with the user's existing Authorization header; done means the behavior is specified and covered by a regression test.

Written by the indexing model from the issue text.