Added MRF.QuietReply which prevents replies to public posts from being published to the timelines

lib/pleroma/web/activity_pub/mrf/quiet_reply.ex

@@ -0,0 +1,55 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2023 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.QuietReply do
+  require Pleroma.Constants
+
+  alias Pleroma.User
+
+  @behaviour Pleroma.Web.ActivityPub.MRF.Policy
+
+  @impl true
+  def history_awareness, do: :auto
+
+  @impl true
+  def filter(
+        %{
+          "type" => "Create",
+          "object" => %{
+            "actor" => actor,
+            "type" => "Note",
+            "to" => to,
+            "cc" => cc,
+            "inReplyTo" => in_reply_to
+          }
+        } = object
+      ) do
+    with true <- is_binary(in_reply_to),
+         false <- match?([], cc),
+         %User{follower_address: followers_collection, local: true} <-
+           User.get_by_ap_id(actor) do
+      updated_to =
+        to
+        |> Kernel.++([followers_collection])
+        |> Kernel.--([Pleroma.Constants.as_public()])
+
+      updated_cc = [Pleroma.Constants.as_public()]
+
+      updated_object =
+        object
+        |> put_in(["object", "to"], updated_to)
+        |> put_in(["object", "cc"], updated_cc)
+
+      {:ok, updated_object}
+    else
+      _ -> {:ok, object}
+    end
+  end
+
+  @impl true
+  def filter(object), do: {:ok, object}
+
+  @impl true
+  def describe, do: {:ok, %{}}
+end