[5.4] Adjust app() to work with the new container changes

[KennedyTedesco]

@taylorotwell Since resolve() is just an alias to app() maybe is time to stop providing it? If you do not think so, please let me know.

[GrahamCampbell]

Please don't delete the resolve function. It's strictly not an alias, because it forces 1 param.

[KennedyTedesco]

@GrahamCampbell Didn't see that way before. My bad. 😊 I have made some adjustments.

[KennedyTedesco]

I know it's not strictly necessary, but I would change the resolve() to something like that:

if (! function_exists('resolve')) {
    /**
     * Resolve a service from the container.
     *
     * @param  string  $name
     * @return mixed
     */
    function resolve($name)
    {
        if(is_null($name)) {
            throw new InvalidArgumentException('You must provide the service name.');
        }

        return app($name);
    }
}