feat: implement authenticateRequest and verifyToken JWKS helper methods

[2ynn]

This PR implements authenticateRequest and verifyToken helper methods.

Notes

• the src/clerk/BackendAPI/Helpers/ folder is .genignored
• unlike in the clerk-sdk-python implementation, the secretKey must be passed manually to the AuthenticateRequestOptions and the bearerAuth value passed during sdk instantiation cannot be reused for convenience.
  (due to $sdkConfiguration being a private member of the Jwks SubSDK class).
• unlike in other implementations (Python, C#, Java) the iat claim is only checked when the nbf claim is not provided

Limitations

• the added helper functions are only applicable for Backend APIs, afterSignInUrl/afterSignUpUrl options are not implemented
• multi-domain setup (isSatellite, proxyUrl, signInUrl, signUpUrl) is not implemented
• caching is not covered by this PR and skipJwksCache option is not made available

Tests

To run all tests (vendor/bin/pint) the following environment variables should be set:

• CLERK_SESSION_TOKEN: The session token to be tested.
• CLERK_SECRET_KEY: The Clerk secret key from the API Keys page in the Clerk Dashboard (needed for fetching Clerk's Jwks)
• CLERK_JWT_KEY: The PEM public key from Clerk Dashboard (needed for networkless verification only)

Example Usage

1. Remote JWKS (using secretKey)

use GuzzleHttp\Psr7\Request;
use Clerk\Backend\Helpers\Jwks\AuthenticateRequestOptions;
use Clerk\Backend\Helpers\Jwks\AuthenticateRequest;
use Clerk\Backend\Helpers\Jwks\RequestState;

class UserAuthentication
{
    public static function isSignedIn(Request $request): bool
    {
        $options = new AuthenticateRequestOptions(
            secretKey: getenv("CLERK_SECRET_KEY"),
            authorizedParties: ["https://example.com"]
        );

        $requestState = AuthenticateRequest::authenticateRequest($request, $options);

        return $requestState.isSignedIn();
    }
}

2. Networkless (using local PEM formatted jwtKey)

<?php

use GuzzleHttp\Psr7\Request;
use Clerk\Backend\Helpers\Jwks\AuthenticateRequestOptions;
use Clerk\Backend\Helpers\Jwks\AuthenticateRequest;
use Clerk\Backend\Helpers\Jwks\RequestState;

class UserAuthentication
{
    public static function isSignedIn(Request $request): bool
    {
        $options = new AuthenticateRequestOptions(
            jwtKey: getenv('CLERK_JWT_KEY'),
            authorizedParties: ['https://example.com']
        );

        $requestState = AuthenticateRequest::authenticateRequest($request, $options);

        return $requestState->isSignedIn();
    }
}