Enable validation for all Things and pick correct branch

This commit updates the branch to use Thing._class_settings instead of FEATURE_FLAGS for a safer way to implement new features.

src/openflexure_microscope_server/things/illumination.py

@@ -12,6 +12,8 @@ from .stage.sangaboard import SangaboardThing
 class Illumination(lt.Thing):
     """Base class for an illumination controller."""
 
+    _class_settings = {"validate_properties_on_set": True}
+
     @lt.action
     def set_led(self, led_on: bool = True) -> None:
         """Set the LED to on or off."""