feat: add support for EXTERNAL auth without uid (#193)

tests/test_auth.py

@@ -3,9 +3,19 @@ import os
 
 import pytest
 
-from dbus_fast.auth import AuthExternal
+from dbus_fast.auth import UID_NOT_SPECIFIED, AuthExternal
+from dbus_fast.errors import AuthError
 
 
 def test_uid_is_set():
     auth = AuthExternal(uid=999)
     assert auth._authentication_start() == "AUTH EXTERNAL 393939"
+
+
+def test_auth_external_no_uid():
+    """Test AuthExternal with UID_NOT_SPECIFIED"""
+    auth = AuthExternal(uid=UID_NOT_SPECIFIED)
+    assert auth._authentication_start() == "AUTH EXTERNAL"
+    assert auth._receive_line("DATA") == "DATA"
+    with pytest.raises(AuthError):
+        auth._receive_line("REJECTED")