[6.x] Add "missing" method to Request class

[TitasGailius]

Just a simple method to check if a given key(s) is missing in the request object.

Instead of doing

if (! $request->has('foo')) {
    //
}

you could do

if ($request->missing('foo')) {
    //
}

[taylorotwell]

Might be worth PRing the laravel/docs repository to document this. Thanks.

[Korko]

Shouldn't it be "misses" instead of "missing" to respect the same naming system as "has"?

[mpryvkin]

Maybe it should have been called doesntHave similar to whereHas/whereDoesntHave?

[TitasGailius]

I think missing is fine. We can already do cache()->missing($key).

[TheNewSound]

I think its ridiculous to make a separate method for 'missing()'. Totally unnecessary overhead. Increases laravel's size, documentation and project code becomes less 'unified' because of different syntax possibilities for exactly the same thing.

If the programmer wants the opposite of has(), its up to him to type !has()
Its faster and cleaner and shorter.