A unique string that identifies the request and that allows failed CreateHostedZone requests to be retried without the risk of
            executing the operation twice. You must use a unique CallerReference string every time you create a hosted zone.
            CallerReference can be any unique string; you might choose to use a string that identifies your project, such as
            DNSMigration_01. Valid characters are any Unicode code points that are legal in an XML 1.0 document. The UTF-8 encoding of the value
            must be less than 128 bytes.
             
            
Constraints:
 Declaration Syntax
 Declaration Syntax| C# | 
public string CallerReference { get; set; }