Let _install_update_win() accept unknown kwargs (#127)

* reproduce issue126 in test

* accept unknown kwargs in _install_update_win

src/tufup/utils/platform_specific.py

@@ -134,6 +134,7 @@ def _install_update_win(
     log_file_name: Optional[str] = None,
     robocopy_options_override: Optional[List[str]] = None,
     process_creation_flags=None,
+    **kwargs,  # noqa
 ):
     """
     Create a batch script that moves files from src to dst, then run the

tests/test_utils_platform_specific.py

@@ -97,7 +97,10 @@ def test_run_bat_as_admin(self):
     def test_install_update_no_purge(self):
         extra_kwargs_strings = []
         if ON_WINDOWS:
-            extra_kwargs_strings.extend(['as_admin=False', 'log_file_name=None'])
+            extra_kwargs_strings.extend(
+                # unknown_kwarg reproduces issue #126
+                ['as_admin=False', 'log_file_name=None', 'unknown_kwarg=True']
+            )
         # run the dummy app in a separate process
         self.run_dummy_app(extra_kwargs_strings=extra_kwargs_strings)
         # ensure file has been moved from src to dst