class Registration  {      Race race     String name     Date dateOfBirth     String gender = 'F'    String postalAddress     String emailAddress     Date createdAt = new Date()     static belongsTo = Race     static optionals = ["postalAddress" ]          static constraints = {             name(maxLength:50,blank:false)         dateOfBirth(nullable:false)         gender(inList:["M", "F"])         postalAddress(maxLength:255)         emailAddress(maxLength:50,email:true)         race(nullable:false)     }                String toString() { "${this.name} : ${this.emailAddress}" }         }