add missing license file

src/main/java/io/lavagna/web/security/login/oauth/OAuth2ServiceImplCustomSignRequest.java

@@ -1,3 +1,19 @@
+/**
+ * This file is part of lavagna.
+ *
+ * lavagna 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 3 of the License, or
+ * (at your option) any later version.
+ *
+ * lavagna 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 lavagna.  If not, see <http://www.gnu.org/licenses/>.
+ */
 package io.lavagna.web.security.login.oauth;
 
 import org.scribe.builder.api.DefaultApi20;