title: How to keep default value in domain with Gorm relationship one-to-one?
body: <p>I can define default value in domain by this way :</p>
  
  <pre><code>class ProcessingPriority {
  
      static constraints = {
      }
  
      String processingPriority = "medium"
  
      String toString()
      {
          return processingPriority
      } 
  }
  </code></pre>
  
  <p>If I'm using this in another domain (using one-to-one), processingPriority is not define to "medium" but "null", ex :</p>
  
  <pre><code>class AnnotationForm {
  
    static belongsTo = ProcessingPriority
    static constraints = {processingPriority()}
  
    ProcessingPriority processingPriority
    ...
  }
  </code></pre>
  
  <p>How can I set my class AnnotationForm to define : String processingPriority = "medium" ?</p>
  
  <p>Is there a best way to define default values in relationship 1to1 ?</p>