How can I basically carry out a unique constraint on a string data-type field.

class User{ String username String Email

static hasMany = [roles:Roles]

 static constraints = {
 Email(email:true)
 username(unique:true)

}

Is there any simple way to implement username(unique:true)

or I will have to manually check the database by the in-built methods like .findByNameLike.

My need is that username should be unique and should be case insensitive