Rework sessions, remember cookies, and auth again

- Use Symfony's Session component to work with sessions, instead of a custom database model. Separate the concept of access tokens from sessions once again.
- Extract common session/remember cookie logic into SessionAuthenticator and Rememberer classes.
- Extract AuthenticateUserTrait into a new AuthenticationResponseFactory class.
- Fix forgot password process.

src/Api/Client.php

@@ -12,7 +12,7 @@ namespace Flarum\Api;
 
 use Flarum\Http\Controller\ControllerInterface;
 use Flarum\Core\User;
-use Flarum\Http\Session;
+use Flarum\Http\AccessToken;
 use Illuminate\Contracts\Container\Container;
 use Exception;
 use InvalidArgumentException;
@@ -44,22 +44,15 @@ class Client
      * Execute the given API action class, pass the input and return its response.
      *
      * @param string|ControllerInterface $controller
-     * @param Session|User|null $session
+     * @param User|null $actor
      * @param array $queryParams
      * @param array $body
      * @return \Psr\Http\Message\ResponseInterface
      */
-    public function send($controller, $session, array $queryParams = [], array $body = [])
+    public function send($controller, $actor, array $queryParams = [], array $body = [])
     {
         $request = ServerRequestFactory::fromGlobals(null, $queryParams, $body);
 
-        if ($session instanceof Session) {
-            $request = $request->withAttribute('session', $session);
-            $actor = $session->user;
-        } else {
-            $actor = $session;
-        }
-
         $request = $request->withAttribute('actor', $actor);
 
         if (is_string($controller)) {