Add config entry and device support to Demo (#28702)

* Add config entry and device support to Demo

* Some more devices

* Fix tests using demo

* Review comments

* Update config_flow.py

* Revert

* Disable pylint

homeassistant/components/demo/binary_sensor.py

@@ -1,26 +1,49 @@
 """Demo platform that has two fake binary sensors."""
 from homeassistant.components.binary_sensor import BinarySensorDevice
+from . import DOMAIN
 
 
-def setup_platform(hass, config, add_entities, discovery_info=None):
+async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
     """Set up the Demo binary sensor platform."""
-    add_entities(
+    async_add_entities(
         [
-            DemoBinarySensor("Basement Floor Wet", False, "moisture"),
-            DemoBinarySensor("Movement Backyard", True, "motion"),
+            DemoBinarySensor("binary_1", "Basement Floor Wet", False, "moisture"),
+            DemoBinarySensor("binary_2", "Movement Backyard", True, "motion"),
         ]
     )
 
 
+async def async_setup_entry(hass, config_entry, async_add_entities):
+    """Set up the Demo config entry."""
+    await async_setup_platform(hass, {}, async_add_entities)
+
+
 class DemoBinarySensor(BinarySensorDevice):
     """representation of a Demo binary sensor."""
 
-    def __init__(self, name, state, device_class):
+    def __init__(self, unique_id, name, state, device_class):
         """Initialize the demo sensor."""
+        self._unique_id = unique_id
         self._name = name
         self._state = state
         self._sensor_type = device_class
 
+    @property
+    def device_info(self):
+        """Return device info."""
+        return {
+            "identifiers": {
+                # Serial numbers are unique identifiers within a specific domain
+                (DOMAIN, self.unique_id)
+            },
+            "name": self.name,
+        }
+
+    @property
+    def unique_id(self):
+        """Return the unique id."""
+        return self._unique_id
+
     @property
     def device_class(self):
         """Return the class of this sensor."""