Make user age limit configurable

Switch to milliseconds for consistency with other configuration options in codebase

config/config.exs

@@ -430,6 +430,8 @@
   mention_parent: true,
   mention_quoted: true
 
+config :pleroma, :mrf_antimentionspam, user_age_limit: 30_000
+
 config :pleroma, :rich_media,
   enabled: true,
   ignore_hosts: [],

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

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Web.ActivityPub.MRF.AntiMentionSpamPolicy do
+  alias Pleroma.Config
   alias Pleroma.User
   require Pleroma.Constants
 
@@ -11,8 +12,9 @@ defmodule Pleroma.Web.ActivityPub.MRF.AntiMentionSpamPolicy do
   defp user_has_posted?(%User{} = u), do: u.note_count > 0
 
   defp user_has_age?(%User{} = u) do
-    diff = NaiveDateTime.utc_now() |> NaiveDateTime.diff(u.inserted_at, :second)
-    diff >= :timer.seconds(30)
+    user_age_limit = Config.get([:mrf_antimentionspam, :user_age_limit], 30_000)
+    diff = NaiveDateTime.utc_now() |> NaiveDateTime.diff(u.inserted_at, :millisecond)
+    diff >= user_age_limit
   end
 
   defp good_reputation?(%User{} = u) do