@API(status = API.Status.STABLE)
        public @NonNull Builder<C> appendHandler(final @NonNull CommandExecutionHandler<C> handler) {
            return this.handler(CommandExecutionHandler.delegatingExecutionHandler(Arrays.asList(this.handler(), handler)));
        }
Sets a new command execution handler that invokes the given {@code handler} after the current
{@link #handler() handler}.

@param handler the handler to invoke after the current handler
@return new builder instance
cloud-core/src/main/java/org/incendo/cloud/Command.java