Google App Engine using UserProperty to bind data

Question

I am writing an application in GAE. To relate the current user to the data in my application, I relied on the equality between users.get_current_user () and members.user (see Model below). When I encounter difficulties, this is when a user signs up with an email address using a different capitalization than his original login ( [e-mail] ! = [e-mail] ). What is the most reliable way to bind the current user to specific application data?

class members(db.Model):
    firstName=db.StringProperty(verbose_name='First Name',required=True)
    lastName=db.StringProperty(verbose_name='Last Name',required=True)
    user=db.UserProperty()

Answer 1

- user.user_id() . , .

Answer 2

, : .