proto(iam): add scope policy storage policy

internal/proto/controller/api/resources/scopes/v1/scope.proto

@@ -87,6 +87,9 @@ message Scope {
 
   // Output only. The authorized actions for the scope's collections.
   map<string, google.protobuf.ListValue> authorized_collection_actions = 310 [json_name = "authorized_collection_actions"];
+
+  // Output only. The attached storage policy id.
+  string storage_policy_id = 320 [json_name = "storage_policy_id"]; // @gotags: `class:"public"`
 }
 
 // KeyVersion describes a specific version of a key and holds the actual key material