Introduce unique_id for lastfm to allow changing entity_id in backwards compatible way (#31163)

* Replace . with _ for lastfm entity_id

* lint

* double quotes

* Rollback change, add unique_id

* Expose prop

* Generate unique ID from user

* Linty

* FIx linter

* Revert changes for splitting entity_id

* Simplify

homeassistant/components/lastfm/sensor.py

@@ -1,4 +1,5 @@
 """Sensor for Last.fm account status."""
+import hashlib
 import logging
 import re
 
@@ -54,8 +55,10 @@ class LastfmSensor(Entity):
 
     def __init__(self, user, lastfm_api):
         """Initialize the sensor."""
+        self._unique_id = hashlib.sha256(user.encode("utf-8")).hexdigest()
         self._user = lastfm_api.get_user(user)
         self._name = user
+        self._entity_id = user
         self._lastfm = lastfm_api
         self._state = "Not Scrobbling"
         self._playcount = None
@@ -63,6 +66,11 @@ class LastfmSensor(Entity):
         self._topplayed = None
         self._cover = None
 
+    @property
+    def unique_id(self):
+        """Return the unique ID of the sensor."""
+        return self._unique_id
+
     @property
     def name(self):
         """Return the name of the sensor."""
@@ -71,7 +79,7 @@ class LastfmSensor(Entity):
     @property
     def entity_id(self):
         """Return the entity ID."""
-        return f"sensor.lastfm_{self._name}"
+        return f"sensor.lastfm_{self._entity_id}"
 
     @property
     def state(self):