Remove use of atoms in MRF.UserAllowListPolicy

lib/pleroma/config/deprecation_warnings.ex

@@ -4,9 +4,10 @@
 
 defmodule Pleroma.Config.DeprecationWarnings do
   require Logger
+  alias Pleroma.Config
 
   def check_hellthread_threshold do
-    if Pleroma.Config.get([:mrf_hellthread, :threshold]) do
+    if Config.get([:mrf_hellthread, :threshold]) do
       Logger.warn("""
       !!!DEPRECATION WARNING!!!
       You are using the old configuration mechanism for the hellthread filter. Please check config.md.
@@ -14,7 +15,29 @@ defmodule Pleroma.Config.DeprecationWarnings do
     end
   end
 
+  def mrf_user_allowlist do
+    config = Config.get(:mrf_user_allowlist)
+
+    if config && Enum.any?(config, fn {k, _} -> is_atom(k) end) do
+      rewritten =
+        Enum.reduce(Config.get(:mrf_user_allowlist), Map.new(), fn {k, v}, acc ->
+          Map.put(acc, to_string(k), v)
+        end)
+
+      Config.put(:mrf_user_allowlist, rewritten)
+
+      Logger.error("""
+      !!!DEPRECATION WARNING!!!
+      As of Pleroma 2.0.7, the `mrf_user_allowlist` setting changed of format.
+      Pleroma 2.1 will remove support for the old format. Please change your configuration to match this:
+
+      config :pleroma, :mrf_user_allowlist, #{inspect(rewritten, pretty: true)}
+      """)
+    end
+  end
+
   def warn do
     check_hellthread_threshold()
+    mrf_user_allowlist()
   end
 end

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

@@ -24,7 +24,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.UserAllowListPolicy do
 
     allow_list =
       Config.get(
-        [:mrf_user_allowlist, String.to_atom(actor_info.host)],
+        [:mrf_user_allowlist, actor_info.host],
         []
       )