Changes to Update Execution Notification

added the new optional request property http_headers

the enabled request property default value true was removed

the execution_contingent request property default value false was removed

the strict_tls request property default value true was removed

added the optional property http_headers to the response with the 200 status

the enabled response's property default value true was removed for the status 200

the execution_contingent response's property default value false was removed for the status 200

the strict_tls response's property default value true was removed for the status 200