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/Http/Controller/ClientView.php

@@ -343,7 +343,7 @@ class ClientView implements Renderable
 
         return [
             'userId' => $this->actor->id,
-            'csrfToken' => $session->csrf_token
+            'csrfToken' => $session->get('csrf_token')
         ];
     }
 }