Implement notifications service with shared messaging and email drivers (#36)

backend/notifications/config.example.yml

@@ -0,0 +1,24 @@
+listen: "127.0.0.1:8083"
+tls_cert: "server.crt"
+tls_key: "server.key"
+database:
+  driver: mongodb
+  settings:
+    uri_env: SXCHNGE_MONGO_URI
+    database: sxchnge_notifications
+messaging:
+  driver: NATS
+  settings:
+    url_env: SXCHNGE_NATS_URL
+    broker_name: sxchnge-notifications
+    max_reconnects: -1
+    reconnect_wait: 2
+templates: "templates.example.json"
+callers:
+  product: "SXCHNGE_NOTIFICATIONS_PRODUCT_TOKEN"
+email:
+  driver: resend # sendgrid or resend
+  settings:
+    api_key_env: "RESEND_API_KEY" # SENDGRID_API_KEY when driver is sendgrid
+    sender_address: "notifications@example.com"
+    sender_name: "SXCHNGE"