Add blog post about changes to UnitOfConductivity (#2357)

blog/2024-10-08-unit-of-conductivity-changes.md

@@ -0,0 +1,31 @@
+---
+author: Erik Montnemery
+authorURL: https://github.com/emontnemery
+title: "Changes to the UnitOfConductivity enum"
+---
+
+The `UnitOfConductivity` enum has been changed from:
+
+```py
+  class UnitOfConductivity(StrEnum):
+    """Conductivity units."""
+
+    SIEMENS = "S/cm"
+    MICROSIEMENS = "µS/cm"
+    MILLISIEMENS = "mS/cm"
+```
+
+To:
+
+```py
+  class UnitOfConductivity(StrEnum):
+    """Conductivity units."""
+
+    SIEMENS_PER_CM = "S/cm"
+    MICROSIEMENS_PER_CM = "µS/cm"
+    MILLISIEMENS_PER_CM = "mS/cm"
+```
+
+The old enum members can be used during a deprecation period of one year, to give time for custom integrations to migrate to the new enum members.
+
+See [core PR #127919](https://github.com/home-assistant/core/pull/127919) for implementation details.