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>
Define `ControlService` for IR similar to the one from storage node. Add
`HealthStatus` RPC which returns health status of the IR application.
Implement getters, setters and methods to sign/verify the messages.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>