Support differing operation tag and undo tag (#1646)

* change returned api name if undo tags are set

* change undo tags to single string

Author: nkzou

src/test/java/com/datadog/api/Undo.java

@@ -23,6 +23,7 @@ public static class Parameter {
       public String template;
     }
 
+    public String tag;
     public String type;
     public String operationId;
     public List<Parameter> parameters;
@@ -79,6 +80,7 @@ public static String toOperationName(String string) {
   }
 
   public String getAPIName() {
+    if (undo.tag != null) return Pattern.compile(" ").matcher(undo.tag).replaceAll("");
     return Pattern.compile(" ").matcher(tag).replaceAll("");
   }