@API(status = API.Status.STABLE)
    protected final void commandRegistrationHandler(final @NonNull CommandRegistrationHandler<C> commandRegistrationHandler) {
        this.requireState(RegistrationState.BEFORE_REGISTRATION);
        this.commandRegistrationHandler = commandRegistrationHandler;
    }
Returns the command registration handler.
<p>
The command registration handler is able to intercept newly created/deleted commands, in order to propagate
these changes to the native command handler of the platform.
<p>
In platforms without a native command concept, this is likely to return
{@link CommandRegistrationHandler#nullCommandRegistrationHandler()}.

@return the command registration handler
cloud-core/src/main/java/org/incendo/cloud/CommandManager.java