title: Groovy / Grails dynamically add a String type field
body: <p>How to add a String type field to class (i.e to all instances of that class), like grails add an id and version fields to all domain classes? If it is possible, how to specify the type of field as String / Long etc </p>
  
  <p>EDIT:</p>
  
  <p>The added fields are not updated in DB. how to make them persistent?</p>