[services-lib] Add HTTP client auth support

Summary:
A proof of concept on how "User Identity" a.k.a commServicesAccessToken can be used with blob client

Depends on D8780.

Test Plan: TBD

Reviewers: michal, jon

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8786