sieve: move cfg.sieveDirectory into home directory of virtual users

default.nix

@@ -1056,14 +1056,6 @@ in
       '';
     };
 
-    sieveDirectory = mkOption {
-      type = types.path;
-      default = "/var/sieve";
-      description = ''
-        Where to store the sieve scripts.
-      '';
-    };
-
     virusScanning = mkOption {
       type = types.bool;
       default = false;
@@ -1795,5 +1787,8 @@ in
     (mkRemovedOptionModule [ "mailserver" "fullTextSearch" "autoIndexExclude" ] ''
       Configure `fts_autoindex` on mail directories in `mailserver.mailboxes` instead.
     '')
+    (mkRemovedOptionModule [ "mailserver" "sieveDirectory" ] ''
+      The Sieve directory has been moved into the virtual Dovecot home directory of each user and can longer be configured.
+    '')
   ];
 }