webui: organize config page with subtabs

tests/test_http_api_contract.py

@@ -352,3 +352,17 @@ def test_embedded_webui_config_page_is_grouped():
     assert "Relay Outputs" in source
     assert "Temperature Assignment" in source
     assert "Maintenance" in source
+
+
+def test_embedded_webui_config_subtabs():
+    source = firmware_source()
+
+    assert "function showConfigSubtab(name)" in source
+    assert "config-general" in source
+    assert "config-wifi" in source
+    assert "config-relays" in source
+    assert "config-temps" in source
+    assert "config-bms" in source
+    assert "config-maintenance" in source
+    assert "WiFi / AP" in source
+    assert "Maintenance" in source