Add support for SendGrid as Email notification handler

src/main/java/io/kamax/mxisd/config/threepid/notification/NotificationConfig.java

@@ -0,0 +1,57 @@
+/*
+ * mxisd - Matrix Identity Server Daemon
+ * Copyright (C) 2017 Maxime Dor
+ *
+ * https://max.kamax.io/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package io.kamax.mxisd.config.threepid.notification;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.context.annotation.Configuration;
+
+import javax.annotation.PostConstruct;
+import java.util.HashMap;
+import java.util.Map;
+
+@Configuration
+@ConfigurationProperties("notification")
+public class NotificationConfig {
+
+    private Logger log = LoggerFactory.getLogger(NotificationConfig.class);
+
+    private Map<String, String> handler = new HashMap<>();
+
+    public Map<String, String> getHandler() {
+        return handler;
+    }
+
+    public void setHandler(Map<String, String> handler) {
+        this.handler = handler;
+    }
+
+    @PostConstruct
+    public void build() {
+        log.info("--- Notification config ---");
+        log.info("Handlers:");
+        handler.forEach((k, v) -> {
+            log.info("\t{}: {}", k, v);
+        });
+    }
+
+}