class User {
  String name

  static hasOne = [emailProfile: EmailProfile]

  static constraints = {
    emailProfile unique: true, nullable: true
  }
}

class EmailProfile {
    String email
    String password

    static belongsTo = [user: User]
}

new User(
  name: 'Bob',
  emailProfile: new EmailProfile(email: 'foo@bar.com', password: 'pass')
).save(failOnError: true)