Merge branch '2257-self-chat' into 'develop'

Resolve "Can't message yourself in a chat (but can start it)"

Closes #2257

See merge request pleroma/pleroma!3099

lib/pleroma/web/activity_pub/side_effects.ex

@@ -306,6 +306,7 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
 
       streamables =
         [[actor, recipient], [recipient, actor]]
+        |> Enum.uniq()
         |> Enum.map(fn [user, other_user] ->
           if user.local do
             {:ok, chat} = Chat.bump_or_create(user.id, other_user.ap_id)