ChatView: Add a mastodon api representation of the recipient.

lib/pleroma/web/activity_pub/transmogrifier/chat_message_handling.ex

@@ -22,6 +22,7 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier.ChatMessageHandling do
          # For now, just strip HTML
          stripped_content = Pleroma.HTML.strip_tags(object_cast_data["content"]),
          object_cast_data = object_cast_data |> Map.put("content", stripped_content),
+         {_, true} <- {:to_fields_match, cast_data["to"] == object_cast_data["to"]},
          {_, {:ok, validated_object, _meta}} <-
            {:validate_object, ObjectValidator.validate(object_cast_data, %{})},
          {_, {:ok, _created_object}} <- {:persist_object, Object.create(validated_object)},

lib/pleroma/web/pleroma_api/views/chat_view.ex

@@ -6,11 +6,16 @@ defmodule Pleroma.Web.PleromaAPI.ChatView do
   use Pleroma.Web, :view
 
   alias Pleroma.Chat
+  alias Pleroma.User
+  alias Pleroma.Web.MastodonAPI.AccountView
+
+  def render("show.json", %{chat: %Chat{} = chat} = opts) do
+    recipient = User.get_cached_by_ap_id(chat.recipient)
 
-  def render("show.json", %{chat: %Chat{} = chat}) do
     %{
       id: chat.id |> to_string(),
       recipient: chat.recipient,
+      recipient_account: AccountView.render("show.json", Map.put(opts, :user, recipient)),
       unread: chat.unread
     }
   end