Add support of service-to-service auth/authz

[artem-v]

Scalecube services in the cluster must be able to communicate between themselves in some authenticated and authorized manner.
Main idea, is that any scalecube service in the cluster is one of those: service-consumer (SC), service-provider (SP), or both (SCP).

SP

• declares roles and permissions on the services.
• assumes that SCs are calling SP APIs using SP roles and permissions.

SC

• communicates with one or many SPs.
• can request a grant to call SP APIs taking in account corresp. roles and permissions.

[artem-v]

Closing. Fixed at #903.