[BREAKING CHANGE 🚨] Change arguments for authorize

[mfn]

For background, see #481 and specifically #481 (comment) and further comments.

The basic change:

• before: public function authorize(array $args): bool
• after: public function authorize($root, array $args, $ctx, ResolveInfo $resolveInfo = null, Closure $getSelectFields = null): bool

The astute reader will recognize that these are exactly the same arguments passed to resolve, and this isn't a coincidence.

This is also made even clearer in the small refactor I did in the code regarding calling them:

            // Authorize
            if (call_user_func_array($authorize, $arguments) != true) {
                throw new AuthorizationError('Unauthorized');
            }

            return call_user_func_array($resolver, $arguments);

The only difference is that checking if the returned value and the (automatic) reaction to it (this fact was never different, but due to aligning the arguments it's now even more clear how this works).

Additional changes:

• Don't merge $arguments[2] (context) into $arguments[1] (args), this seems like a strange thing to do, another one of those implicit behaviours without clear indication as to way (blame didn't offer me much more insights)
• Remove method_exists for getRules, that method is already there and can never be "not there"

TODO

• Add a test making use of all args

[mfn]

Pinging all involved in #481 for feedback @illambo @rebing @fvdung

FTR, I did not go down the suggestion with the trait, I simply couldn't see how this would improve things.

[mfn]

Removed, see PR desciption

[mfn]

Best use ?w=1 to see the changes without whitespace

[mfn]

Moved down from before "selects and relations" block to include SelectFields too

[rebing]

Makes sense to change it like this. How will we version it now - 3.0?

[mfn]

How will we version it now - 3.0?

Yes, absolutely has to be!

Actually also for #487 => changing the behaviour what kind of exception will be "reported" is also breaking semvar (IMHO / AFAIK)