Add comprehensive documentation and unit tests

Documentation:
- Add detailed README files for all services (auth, character, database, launcher, packet, utils, world)
- Create API documentation for the database service with detailed endpoint specifications
- Document database schema and relationships
- Add service architecture overviews and configuration instructions

Unit Tests:
- Implement comprehensive test suite for database repositories (user, character, session)
- Add gRPC service tests for database interactions
- Create tests for packet service components (bufferpool, connection, packets)
- Add utility service tests (health check, logging, load balancer, redis cache, service discovery)
- Implement auth service user tests
- Add character service tests

Code Structure:
- Reorganize test files into a more consistent structure
- Create a dedicated tests crate for integration testing
- Add test helpers and mock implementations for easier testing

utils/src/health_check.rs

@@ -12,14 +12,7 @@ pub async fn start_health_check(service_address: &str) -> Result<(), Box<dyn std
         .map(|| warp::reply::with_status("OK", warp::http::StatusCode::OK))
         .with(log);
 
-    tokio::spawn(
-        warp::serve(health_route).run(
-            health_check_endpoint_addr
-                .to_socket_addrs()?
-                .next()
-                .unwrap(),
-        ),
-    );
+    tokio::spawn(warp::serve(health_route).run(health_check_endpoint_addr.to_socket_addrs()?.next().unwrap()));
 
     Ok(())
 }