[FEATURE] Implement trusted header auth

As per topic:

1. Let's user foo@bar.org logging in if a trusted header (eg: HTTP_AUTH_USER) is detected with value: foo@bar.org)
2. decide or not if in the case user does not exists it should be created
3. if the user exists then let him logged in

Reason: Should let pathcmon web ui universally compatible with more idp and sso solutions.