First authenticates the {@code AuthenticationToken} argument, and if successful, constructs a
{@code Subject} instance representing the authenticated account's identity.
<p/>
Once constructed, the {@code Subject} instance is then {@link #bind bound} to the application for
subsequent access before being returned to the caller.
@param token the authenticationToken to process for the login attempt.
@return a Subject representing the authenticated user.
@throws AuthenticationException if there is a problem authenticating the specified {@code token}.
First authenticates the {@code AuthenticationToken} argument, and if successful, constructs a {@code Subject} instance representing the authenticated account's identity. <p/> Once constructed, the {@code Subject} instance is then {@link #bind bound} to the application for subsequent access before being returned to the caller.
@param token the authenticationToken to process for the login attempt. @return a Subject representing the authenticated user. @throws AuthenticationException if there is a problem authenticating the specified {@code token}.