Add explicit support for Luxembourg Smarty meter in dsmr integration (#43975)

* Add support for Luxembourg Smarty meter

* Add config flow test

* Add sensor tests

tests/components/dsmr/test_config_flow.py

@@ -242,3 +242,26 @@ async def test_options_flow(hass):
         await hass.async_block_till_done()
 
     assert entry.options == {"time_between_update": 15}
+
+
+async def test_import_luxembourg(hass, dsmr_connection_send_validate_fixture):
+    """Test we can import."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+
+    entry_data = {
+        "port": "/dev/ttyUSB0",
+        "dsmr_version": "5L",
+        "precision": 4,
+        "reconnect_interval": 30,
+    }
+
+    with patch("homeassistant.components.dsmr.async_setup_entry", return_value=True):
+        result = await hass.config_entries.flow.async_init(
+            DOMAIN,
+            context={"source": config_entries.SOURCE_IMPORT},
+            data=entry_data,
+        )
+
+    assert result["type"] == "create_entry"
+    assert result["title"] == "/dev/ttyUSB0"
+    assert result["data"] == {**entry_data, **SERIAL_DATA}