Completely restored authorization_code grant for user side.

Reworked oauth_sessions table.
Added extension to use MariaDB's JSON columns.
Rewritten tests for authorization_code grant for client side.
Deprecate some old shit.
[skip ci]

api/components/OAuth2/Repositories/ClientRepository.php

@@ -29,8 +29,6 @@ class ClientRepository implements ClientRepositoryInterface {
             return false;
         }
 
-        // TODO: there is missing behavior of checking redirectUri. Is it now bundled into grant?
-
         return true;
     }