Add API/CLI for managed groups (#1265)

internal/proto/local/controller/api/resources/managedgroups/v1/managed_group.proto

@@ -43,6 +43,9 @@ message ManagedGroup {
 	// The attributes that are applicable for the specific ManagedGroup type.
 	google.protobuf.Struct attributes = 100 [(custom_options.v1.generate_sdk_option) = true];
 
+	// Output only. The IDs of the current set of members (accounts) that are associated with this ManagedGroup.
+	repeated string member_ids = 110 [json_name="member_ids"];
+
 	// Output only. The available actions on this resource for this user.
 	repeated string authorized_actions = 300 [json_name="authorized_actions"];
 }