SideEffects / ChatView: Add an unread cache.

This is to prevent wrong values in the stream.

lib/pleroma/web/activity_pub/side_effects.ex

@@ -142,6 +142,11 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
           {:ok, chat} = Chat.bump_or_create(user.id, other_user.ap_id)
           {:ok, cm_ref} = ChatMessageReference.create(chat, object, user.ap_id != actor.ap_id)
 
+          # We add a cache of the unread value here so that it doesn't change when being streamed out
+          chat =
+            chat
+            |> Map.put(:unread, ChatMessageReference.unread_count_for_chat(chat))
+
           Streamer.stream(
             ["user", "user:pleroma_chat"],
             {user, %{cm_ref | chat: chat, object: object}}