Conversations: Add a function to 'import' old DMs.

lib/pleroma/conversation.ex

@@ -72,4 +72,18 @@ defmodule Pleroma.Conversation do
       e -> {:error, e}
     end
   end
+
+  @doc """
+  This is only meant to be run by a mix task. It creates conversations/participations for all direct messages in the database.
+  """
+  def bump_for_all_activities() do
+    stream =
+      Pleroma.Web.ActivityPub.ActivityPub.fetch_direct_messages_query()
+      |> Repo.stream()
+
+    Repo.transaction(fn ->
+      stream
+      |> Enum.each(&create_or_bump_for/1)
+    end)
+  end
 end

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -1061,4 +1061,10 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
       contain_activity(activity, user)
     end)
   end
+
+  def fetch_direct_messages_query() do
+    Activity
+    |> restrict_type(%{"type" => "Create"})
+    |> restrict_visibility(%{visibility: "direct"})
+  end
 end