The Firebase app instance.
Optionaldeps: anyOptional. Dependencies for the Auth instance.
The Auth instance.
getAuth uses platform-specific defaults to supply the Dependencies. In general, getAuth is the easiest way to initialize Auth and works for most use cases. Use initializeAuth if you need control over which persistence layer is used, or to minimize bundle size if you're not using either signInWithPopup or signInWithRedirect.
This function allows more control over the Auth instance than getAuth().