public abstract string[] always_writeable_properties { get; }

The names of the properties of the Personas in this store which are always writeable.

If a property name is in this list, setting the property on a persona should result in the updated value being stored in the backend's permanent storage (unless it gets rejected due to being invalid, or a different error occurs).

This property value is guaranteed to be constant for a given persona store, but may vary between persona stores in the same backend. It's guaranteed that this will always be a subset of the value of Persona.writeable_properties for the personas in this persona store.