Add dsmr_reader telegram timestamp and device classes (#42909)

* Added Telegram timestamp

* added to 'dsmr/reading/timestamp' and 'dsmr/consumption/gas/read_at'

* Fixed import sorting

* Replaced 'kW' with ENERGY_KILO_WATT_HOUR

* Added device_class, changed unit_of_measurement with fallback on device_class

* Fixed typo

* Fixed 'black' coding format

* Removed fallback, added unit_of_measurement and CURRENCY_EURO as device_class

* Fixed newline

* Removed 'timestamp' unit_of_meassure

* Removed icons from defintions with device_class

* Updated device_classes

* Updated device_classes

* Updated device_classes

* Added 'entity_registry_enabled_default' properties

* Added 'entity_registry_enabled_default' properties, fixed typo

* MQTT discovery will be in another pull-request

homeassistant/components/dsmr_reader/sensor.py

@@ -31,6 +31,8 @@ class DSMRSensor(Entity):
         self._topic = topic
 
         self._name = self._definition.get("name", topic.split("/")[-1])
+        self._device_class = self._definition.get("device_class")
+        self._enable_default = self._definition.get("enable_default")
         self._unit_of_measurement = self._definition.get("unit")
         self._icon = self._definition.get("icon")
         self._transform = self._definition.get("transform")
@@ -67,11 +69,21 @@ class DSMRSensor(Entity):
         """Return the current state of the entity."""
         return self._state
 
+    @property
+    def device_class(self):
+        """Return the device_class of this sensor."""
+        return self._device_class
+
     @property
     def unit_of_measurement(self):
         """Return the unit_of_measurement of this sensor."""
         return self._unit_of_measurement
 
+    @property
+    def entity_registry_enabled_default(self) -> bool:
+        """Return if the entity should be enabled when first added to the entity registry."""
+        return self._enable_default
+
     @property
     def icon(self):
         """Return the icon of this sensor."""