[#401] control: Add RPC to mark objects to be removed from the node

There is a need to define storage node's interface to remove objects from
the local storage.

Define `DropObjects` RPC in `ControlService`. Define `DropObjectsRequest` /
`DropObjectsResponse` structure of the request / response messages.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/control/service.proto

@@ -16,6 +16,9 @@ service ControlService {
 
     // Sets status of the storage node in NeoFS network map.
     rpc SetNetmapStatus (SetNetmapStatusRequest) returns (SetNetmapStatusResponse);
+
+    // Mark objects to be removed from node's local object storage.
+    rpc DropObjects (DropObjectsRequest) returns (DropObjectsResponse);
 }
 
 // Health check request.
@@ -104,3 +107,32 @@ message SetNetmapStatusResponse {
     // Body signature.
     Signature signature = 2;
 }
+
+// Request to drop the objects.
+message DropObjectsRequest {
+    // Request body structure.
+    message Body {
+        // List of object addresses to be removed.
+        // in NeoFS API binary format.
+        repeated bytes address_list = 1;
+    }
+
+    // Body of the request message.
+    Body body = 1;
+
+    // Body signature.
+    Signature signature = 2;
+}
+
+// Response to request to drop the objects.
+message DropObjectsResponse {
+    // Response body structure.
+    message Body {
+    }
+
+    // Body of the response message.
+    Body body = 1;
+
+    // Body signature.
+    Signature signature = 2;
+}