I'm glad you've included GenericPrincipal for the common username/password authentication scheme. However, there is one big issue.

When I want to inherit Person/Customer/etc. from GenericPrincipal, the Name property should not be used as the username - it should instead be the full name for the Person/Customer. I'd instead like to specify a different property to be used as the authenticating username.

Also, this is important for cases where I want to use the email as the authenticating username.

For example:

[AuthenticationUsername("Email")]
public class Customer : GenericPrincipal {
  [Field]
  public string Name { get; set; } // This should be the customer's real name, e.g. "Joe Smith"

  [Field, AuthenticationUsername]
  public string Email { get; set; } // I want to use this as the customer's login credential

  // public string PasswordHash { get; set; } // This should be inherited from GenericPrincipal, as is the case
}

Moreover, there are many cases where I don't want all Persons/Customers to have login access. Therefore, it should be possible to leave Email nullable. So, there should NOT be a UNIQUE index applied to Email, because multiple Customers could have null emails (I may not know many of their emails)... unless we apply a FILTERED unique index for non-null values.

This is very important for my project. How long would it take to implement this?