Remove policy-spf

Rspamd can do the same as policy-spf, only better, with more settings, is well integrated and better maintained.
Other projects are going the same route [1].

[1]: https://docker-mailserver.github.io/docker-mailserver/latest/config/best-practices/dkim_dmarc_spf/

default.nix

@@ -1022,18 +1022,6 @@ in
       '';
     };
 
-    policydSPFExtraConfig = mkOption {
-      type = types.lines;
-      default = "";
-      example = ''
-        skip_addresses = 127.0.0.0/8,::ffff:127.0.0.0/104,::1
-      '';
-      description = ''
-        Extra configuration options for policyd-spf. This can be use to among
-        other things skip spf checking for some IP addresses.
-      '';
-    };
-
     monitoring = {
       enable = mkEnableOption "monitoring via monit";
 
@@ -1303,7 +1291,6 @@ in
     '')
     ./mail-server/assertions.nix
     ./mail-server/borgbackup.nix
-    ./mail-server/debug.nix
     ./mail-server/rsnapshot.nix
     ./mail-server/clamav.nix
     ./mail-server/monit.nix
@@ -1317,5 +1304,9 @@ in
     ./mail-server/rspamd.nix
     ./mail-server/nginx.nix
     ./mail-server/kresd.nix
+    (lib.mkRemovedOptionModule [ "mailserver" "policydSPFExtraConfig" ] ''
+      SPF checking has been migrated to Rspamd, which makes this config redundant. Please look into the rspamd config to migrate your settings.
+      It may be that they are redundant and are already configured in rspamd like for skip_addresses.
+    '')
   ];
 }