added driftable metadata (#356)

Author: ammokhov

src/main/java/software/amazon/cloudformation/AbstractWrapper.java

@@ -263,6 +263,7 @@ public void processRequest(final InputStream inputStream, final OutputStream out
             resourceHandlerRequest.setStackId(getStackId(request));
             resourceHandlerRequest.setSnapshotRequested(request.getSnapshotRequested());
             resourceHandlerRequest.setRollback(request.getRollback());
+            resourceHandlerRequest.setDriftable(request.getDriftable());
             if (request.getRequestData() != null) {
                 resourceHandlerRequest.setPreviousSystemTags(request.getRequestData().getPreviousSystemTags());
             }

src/main/java/software/amazon/cloudformation/proxy/HandlerRequest.java

@@ -36,5 +36,6 @@ public class HandlerRequest<ResourceT, CallbackT> {
     private CallbackT callbackContext;
     private Boolean snapshotRequested;
     private Boolean rollback;
+    private Boolean driftable;
     private RequestContext<CallbackT> requestContext;
 }

src/main/java/software/amazon/cloudformation/proxy/ResourceHandlerRequest.java

@@ -45,6 +45,7 @@ public class ResourceHandlerRequest<T> {
     private String nextToken;
     private Boolean snapshotRequested;
     private Boolean rollback;
+    private Boolean driftable;
     private String region;
     private String stackId;
 }