Add Export message type to ThingType protocol

Author: haikalpribadi

common/concept.proto

@@ -329,6 +329,7 @@ message Type {
             ThingType.GetPlaysOverridden.Req thing_type_get_plays_overridden_req = 313; // TODO: reorder
             ThingType.SetPlays.Req thing_type_set_plays_req = 307;
             ThingType.UnsetPlays.Req thing_type_unset_plays_req = 308;
+            ThingType.Export.Req thing_type_export_req = 314; // TODO: reorder
 
             // EntityType method requests
             EntityType.Create.Req entity_type_create_req = 400;
@@ -369,6 +370,7 @@ message Type {
             ThingType.GetPlaysOverridden.Res thing_type_get_plays_overridden_res = 307; // TODO: reorder
             ThingType.SetPlays.Res thing_type_set_plays_res = 304;
             ThingType.UnsetPlays.Res thing_type_unset_plays_res = 305;
+            ThingType.Export.Res thing_type_export_res = 308; // TODO: reorder
 
             // EntityType method responses
             EntityType.Create.Res entity_type_create_res = 400;
@@ -623,6 +625,13 @@ message ThingType {
         }
         message Res {}
     }
+
+    message Export {
+        message Req {}
+        message Res {
+            string schema = 1;
+        }
+    }
 }
 
 // EntityType methods