Implement #183: Add ES256 support for Apple Push Notifications

[beamerblvd]

Apple Push Notifications require the JWT algorithm be ES256. It still uses OpenSSL and SHA256 just like RS256, but the algorithm name in the headers must be "ES256" or else the token is rejected as invalid. This simple change adds support for ES256 and improves documentation regarding supported algorithms, which should close #183. I tested this locally, and this change alone allowed me to sent APNs, while I could not without this change.

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[beamerblvd]

I signed it!

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[aaronpk]

Looks great, what's the holdup on merging this?

[bluefirex]

Also waiting for this to get merged. Desperately needed!

[jerome2710]

Can this be merged and published soon?

[carere]

Plz Merge this, i need it for Sign in With Apple. What can it be merged ??? Can you communicate about this ???

[jerome2710]

Since the array is public, you could extend the library in the meantime and overwrite the array:

<?php

namespace your\namespace;

class JWT extends \Firebase\JWT\JWT
{
    public static $supported_algs = [
        'ES256' => ['openssl', 'SHA256'],
        'HS256' => ['hash_hmac', 'SHA256'],
        'HS512' => ['hash_hmac', 'SHA512'],
        'HS384' => ['hash_hmac', 'SHA384'],
        'RS256' => ['openssl', 'SHA256'],
        'RS384' => ['openssl', 'SHA384'],
        'RS512' => ['openssl', 'SHA512'],
    ];
}