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/logging.rs

@@ -4,23 +4,21 @@ use tracing_subscriber::EnvFilter;
 
 pub fn setup_logging(app_name: &str, additional_crates: &[&str]) {
     let log_level = env::var("LOG_LEVEL").unwrap_or_else(|_| "info".to_string());
-    
+
     let mut filter_string = format!("{app_name}={log_level},utils={log_level}");
-    for (crate_name) in additional_crates {
+    for &crate_name in additional_crates {
         filter_string.push(',');
         filter_string.push_str(&format!("{crate_name}={log_level}"));
     }
 
-    let filter = EnvFilter::try_new(filter_string)
-        .unwrap_or_else(|_| EnvFilter::new(format!("{app_name}=info,utils=info")));
-    
-    tracing_subscriber::fmt()
-        .with_env_filter(filter)
-        .init();
-    
+    let filter =
+        EnvFilter::try_new(filter_string).unwrap_or_else(|_| EnvFilter::new(format!("{app_name}=info,utils=info")));
+
+    tracing_subscriber::fmt().with_env_filter(filter).init();
+
     error!("Error messages enabled");
     warn!("Warning messages enabled");
     info!("Info messages enabled");
     debug!("Debug messages enabled");
     trace!("Trace messages enabled");
-}
+}