SendGrid plugin (#77)

Closes #73 and #77

packages/medusa-plugin-sendgrid/src/subscribers/user.js

@@ -0,0 +1,23 @@
+class UserSubscriber {
+  constructor({ sendgridService, eventBusService }) {
+    this.sendgridService_ = sendgridService
+
+    this.eventBus_ = eventBusService
+
+    this.eventBus_.subscribe("user.password_reset", async (data) => {
+      await this.sendgridService_.transactionalEmail(
+        "user.password_reset",
+        data
+      )
+    })
+
+    this.eventBus_.subscribe("customer.password_reset", async (data) => {
+      await this.sendgridService_.transactionalEmail(
+        "customer.password_reset",
+        data
+      )
+    })
+  }
+}
+
+export default UserSubscriber