Handle fetching and saving user specific data, e.g. settings or other state data that should persist between sessions
Get user data
the data
name of the key containing the data
Check if user data exists
true if user data exists
Set user data
a promise that will be resolved when the data has been saved
name of the key for the data
Optional
the data to save, will delete the data if undefined
Subscribe to state changes
unsubscribe callback
function to call when subscription updates
Rest
options for the state selector
Handle fetching and saving user specific data, e.g. settings or other state data that should persist between sessions