Fixing spelling error among all services

README.md

@@ -68,7 +68,7 @@ Messages sent to the backend service:
 
 ```json
 {
-  "receipent_user_id": 1,
+  "user_id": 1,
   "message": {
     "title": "New Life As A Max Level Archmage",
     "body": "Chapter 68 has been released",
@@ -91,4 +91,4 @@ Content-Type: application/json
 
 Available at `http://localhost:9000/metrics`:
 
-- `http_requests_total{method, path, status}`: Request counter with labels
+- `http_requests_total{method, path, status}`: Request counter with labels