Add local_ip component (#29973)

* Added localip component

* Split config and core logic, and migrate to sensor platform (requested by @MartinHjelmare)
Also allow overriding the sensor name via the config

* Tweak docstring

Co-Authored-By: Fabian Affolter <mail@fabian-affolter.ch>

* Initial support for config entries

* Rename localip to local_ip (1/2)

* Rename localip to local_ip (2/2)

* Add test for config_flow

* Split and rename tests

* Remove unneeded code from config_flow

* Implement configuration as config entry import.  Other misc requested changes from code review.

* Fix tests

* minor code review fixes

* remove unneeded code

Co-authored-by: Fabian Affolter <mail@fabian-affolter.ch>

homeassistant/components/local_ip/sensor.py

@@ -0,0 +1,34 @@
+"""Sensor platform for local_ip."""
+
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers.entity import Entity
+from homeassistant.util import get_local_ip
+
+
+async def async_setup_entry(hass: HomeAssistant, config_entry, async_add_entities):
+    """Set up the platform from config_entry."""
+    name = config_entry.data["name"]
+    async_add_entities([IPSensor(name)], True)
+
+
+class IPSensor(Entity):
+    """A simple sensor."""
+
+    def __init__(self, name: str):
+        """Initialize the sensor."""
+        self._state = None
+        self._name = name
+
+    @property
+    def name(self):
+        """Return the name of the sensor."""
+        return self._name
+
+    @property
+    def state(self):
+        """Return the state of the sensor."""
+        return self._state
+
+    def update(self):
+        """Fetch new state data for the sensor."""
+        self._state = get_local_ip()