Header.php

<?php

namespace Http\Message\Authentication;

use Http\Message\Authentication;
use Psr\Http\Message\RequestInterface;

class Header implements Authentication
{
    /**
     * @var string
     */
    private $name;

    /**
     * @var string|string[]
     */
    private $value;

    /**
     * @param string|string[] $value
     */
    public function __construct(string $name, $value)
    {
        $this->name = $name;
        $this->value = $value;
    }

    public function authenticate(RequestInterface $request)
    {
        return $request->withHeader($this->name, $this->value);
    }
}