fix: add missing header

solidify-authorization-server/src/main/java/ch/unige/solidify/auth/filter/SessionKillerFilter.java

+/*-
+ * %%----------------------------------------------------------------------------------------------
+ * Solidify Authorization - Solidify Authorization Server - SessionKillerFilter.java
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * %----------------------------------------------------------------------------------------------%
+ * Copyright (C) 2017 - 2023 University of Geneva
+ * %----------------------------------------------------------------------------------------------%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/gpl-2.0.html>.
+ * ----------------------------------------------------------------------------------------------%%
+ */
+
 package ch.unige.solidify.auth.filter;
 
 import java.io.IOException;