title: How to assign default value for Enum type
body: <p>From this Go code, I am generating the CRD yaml. I am using following structure in Go.
  I want to assign default value for parameters 'Size' and 'Case' from one of the enum options.
  Assigning // +kubebuilder:validation:default:=512 does not take effect in generated yaml file.
  Is there any way in kubebuilder, we can assign default value for enum?</p>
  <pre><code>type Options struct {
      // +kubebuilder:validation:default:=512
      // +kubebuilder:validation:Enum=64;128;256;512
      Size int64 `json:&quot;Size&quot;`
      
      // +kubebuilder:validation:Enum=caseA;caseB
      // +kubebuilder:validation:default:=caseA
      Case string `json:&quot;case&quot;`
  }   
  
  
  
  Generated yaml without default value
  ---------------
   case:
       enum:
        - caseA
        - caseB
       type: string
  
   Size:
       enum:
        - 64
        - 128
        - 256
        -512
       format: int64
       type: integer
  </code></pre>