refactor: make webspeiseplan fetching explicit

tests/test_swp_webspeiseplan_api.py

@@ -0,0 +1,12 @@
+# -*- encoding: utf-8 -*-
+
+from stw_potsdam.swp_webspeiseplan_api import SWPWebspeiseplanAPI
+
+# pytest fixtures are linked via parameter names of test methods
+# pragma pylint: disable=unused-import,unused-argument,redefined-outer-name
+from tests.stub_api import api_offline
+
+
+def test_api_init_does_not_fetch(api_offline):
+    """Creating the API client does not perform network requests."""
+    SWPWebspeiseplanAPI()