Work around upserting problems in context mapping.

lib/pleroma/object.ex

@@ -43,6 +43,6 @@ def get_cached_by_ap_id(ap_id) do
   end
 
   def context_mapping(context) do
-    %Object{data: %{"id" => context}}
+    Object.change(%Object{}, %{data: %{"id" => context}})
   end
 end

lib/pleroma/web/twitter_api/twitter_api.ex

@@ -285,8 +285,12 @@ def context_to_conversation_id(context) do
       id
       else _e ->
         changeset = Object.context_mapping(context)
-      {:ok, %{id: id}} = Repo.insert(changeset)
-      id
+        case Repo.insert(changeset) do
+          {:ok, %{id: id}} -> id
+          # This should be solved by an upsert, but it seems ecto
+          # has problems accessing the constraint inside the jsonb.
+          {:error, _} -> Object.get_cached_by_ap_id(context).id
+        end
     end
   end