Serve `ControlService` instance on configured endpoint (do not serve if not
specified). Read allowed keys from config.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
Implement `ControlServiceServer` on `Server` type. The `Server` requires all
requests to be signed with keys from the so-called whitelist. To obtain
health status, it uses the abstraction in the form of `HealthChecker`
interface.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
