Add ability to add additional information to jwt

[jeremiebourque]

This project works great at adding non-registered claims but it would be nice to expand the functionality to include ways to modify the jwt because it would make no sense to override the token once again and create a redundant jwt builder process.

If for example this is set:

<?php

namespace App\Claims;

class CustomClaims
{
    public function handle($token, $next)
    {
        $token->addClaim('iss', 'https://localhost:8080');

        return $next($token);
    }

The resulting error will be

    {
    "status": 422,
    "message": "Builder#withClaim() is meant to be used for non-registered claims, check the documentation on how to set claim \"iss\""
}

If I would have downloaded this library for the sole purpose of writing an iss claim, then I'm out-of-luck.
The iss could be set with a $token->issuedBy('http://example.com') method.

Similarly, this library does not allow you to set jwt headers which might be required for openid connect.
For example, a header of

{
...
"kid": 'bar'
}

cannot be set because the $token->withHeader('kid', 'bar') cannot be called.

[driesvints]

You can already do this by overriding the Token model: https://laravel.com/docs/9.x/passport#overriding-default-models

[abublihi]

why not the iss claim is set by default?