Adding separate entity username and password fields

[adamvr]

Summary

This pull request adds the options entityUsernameField and entityPasswordField, corresponding to the fields on the user entity that contain the username and password fields respectively. If these options are not defined the username and password fields default back to usernameField and passwordField, maintaining backwards compatibility. This allows the separation of the {username,password}Fields on the user entity and on the incoming authentication request.

Concretely, this allows the following use case:

authentication-local options:

{
  entityUsernameField: 'services.email.address',
  entityPasswordField: 'services.email.password'
}

authentication request:

{
  strategy: 'local',
  username: 'test@email.com',
  password: 'test'
}

user entity:

{
  services: {
    email: {
      address: 'test@email.com'
      password: 'test'
    }
  }
}

Open questions

• Are the field names correct?
• Is it preferable to do it the other way round? requestUsernameField instead of entityUsernameField? Or all three?

[marshallswain]

Thanks for the solid PR!

[ekryski]

Yup thank you! @marshallswain I think this should be good to merge and release as well. :shipit: