adding new sendgrid adapter

lib/notification/adapter/sendGrid.js

@@ -0,0 +1,28 @@
+const sgMail = require('@sendgrid/mail');
+
+/**
+ * sends a new listing using SendGrid
+ * @param serviceName e.g immoscout
+ * @param newListings an array with newly found listings
+ * @param notificationConfig config of this notification adapter
+ * @returns {Promise<Chat.PostMessage.Response> | void}
+ */
+exports.send = (serviceName, newListings, notificationConfig) => {
+  const { apiKey, enabled, receiver, from, templateId } = notificationConfig.sendGrid;
+  if (!enabled) {
+    return [Promise.resolve()];
+  }
+  sgMail.setApiKey(apiKey);
+  const msg = {
+    templateId,
+    to: receiver,
+    from,
+    subject: `Service ${serviceName} found ${newListings.length} new listing(s)`,
+    dynamic_template_data: {
+      serviceName,
+      numberOfListings: newListings.length,
+      listings: newListings,
+    },
+  };
+  return sgMail.send(msg);
+};