[10.x] Fix Stringable objects not converted to string in HTTP facade Query parameters and Body

[LasseRafn]

Seems that in the HTTP Facade, query parameters, json and form bodies cannot process Stringable values, which means they must be cast to string before using.

Here is a failing sample code to use:

\Illuminate\Support\Facades\Http::get( 'https://jsonplaceholder.typicode.com/posts', [
        'id' => \Illuminate\Support\Str::of('99'),
] )->json();

The final url is: https://jsonplaceholder.typicode.com/posts

Notice how the payload contains a lot of data, and including results with a ID differently than 99.

Here is a 'passing' sample code to use:

\Illuminate\Support\Facades\Http::get( 'https://jsonplaceholder.typicode.com/posts', [
        'id' => '99',
] )->json();

The final url is: https://jsonplaceholder.typicode.com/posts?id=99

Notice how there is only one result, which is ID = 99.

Essentially for query parameters and body, Stringable is not handled and is silently ignored, entirely not sending that parameter at all.

I am not fully versed in the PendingRequest logic, and I apologise if this is the wrong approach to handling this. my PR can be treated as a WIP solution / showcase of the issue, that can spawn another PR to solve it more elegantly if the current solution isn't ideal!

---

Additionally, if a Number class similar to Stringable is added (#48845) I suggest we also ensure that it is supported here 👍🏻. Right now I see that it is a helper class, so not relevant, yet?.. just thought to point it out!

[LasseRafn]

Not a gigantic fan of this implementation.

Super happy for someone to come up with a more elegant approach!

[henzeb]

There's a build in stringable interface. But then you could just cast anything coming true to string instead of using the method. One caveat would be the boolean bug though.