Add support for external email domain blocklist

Author: L-e-x-o-n

lib/teiserver/moderation/tasks/load_banned_domains_task.ex

@@ -2,19 +2,35 @@ defmodule Teiserver.Moderation.LoadBannedDomainsTask do
   @moduledoc """
   Loads the list of banned domains from the database into the cache.
   """
+  alias Req.Response
   alias Teiserver.Helpers.CacheHelper
   alias Teiserver.Moderation
   alias Teiserver.Moderation.BannedDomain
 
   def perform do
-    banned_domains =
+    url = Config.get_site_config_cache("teiserver.Email domain blocklist URL")
+
+    external_banned_domains =
+      with true <- url != nil and url != "",
+           {:ok, %Response{status: 200, body: body}} <- Req.get(url) do
+        String.split(body, "\n")
+      else
+        {:error, error} ->
+          Logger.error("Error loading VPN list - #{inspect(error)}")
+          []
+
+        _any ->
+          []
+      end
+
+    internal_banned_domains =
       Moderation.list_banned_domains()
       |> Enum.map(fn %BannedDomain{domain: domain} -> domain end)
 
     CacheHelper.store_put(
       :application_metadata_cache,
       "banned_domains",
-      banned_domains
+      external_banned_domains ++ internal_banned_domains
     )
   end