Models an attempt to sign-in to the application using a provider user identity.
Instances are created when the provider sign-in process could not be completed because no local user is associated with the provider user.
This could happen because the user has not yet signed up with the application, or has not yet connected their local application identity with the their provider identity.
For the former scenario, callers should invoke addConnection(String) post-signup to establish a connection between a new user account and the provider account.
For the latter, existing users should sign-in using their local application credentials and formally connect to the provider they also wish to authenticate with.
Get the connection to the provider user account the client attempted to sign-in as.
Using this connection you may fetch a provider user profile and use that to pre-populate a local user registration/signup form.
You can also lookup the id of the provider and use that to display a provider-specific user-sign-in-attempt flash message e.g. "Your Facebook Account is not connected to a Local account. Please sign up."