A structure containing additional user information from a federated identity provider via
const userCredential = await firebase.auth().signInAnonymously(); console.log('Additional user info: ', userCredential.additionalUserInfo);
Returns whether the user is new or existing.
Returns an Object containing IDP-specific user data if the provider is one of Facebook, GitHub, Google, Twitter, Microsoft, or Yahoo.
profile: Record<string, any>;
Returns the provider ID for specifying which provider the information in
profile is for.
Returns the username if the provider is GitHub or Twitter.
username: undefined | string;