getId

Get the id for an object. If object doesn't implement Identifiable then `fallbackGetId`
must be provided or an error will be thrown.

item

Function to return id for `item` if it doesn't implement Identifiable


fallbackGetId

_key

Interface for types that we can automatically extract a unique identifier from.

To confirm to the interface provide a `_key` property or getter.

[ViewModelFactory](doc:viewModelFactory) conforms to this so anything that expects an Identifiable
will accept a ViewModel.

Implementing this can save you having to pass explicit functions to identify an item in other parts of the system
(eg. for [AsyncChoices](doc:AsyncChoices) or [useAsyncValue](doc:useAsyncValue))


	Parameter	Type	Description
*	item	Identifiable\|any	Any value to get ID for
	fallbackGetId	Function	Function to return id for `item` if it doesn't implement Identifiable