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

database-service/src/grpc/session_service.rs

@@ -1,21 +1,22 @@
 use crate::grpc::database_service::MyDatabaseService;
 use crate::grpc::session_service_server::SessionService;
+use crate::grpc::{GetSessionRequest, GetSessionResponse, RefreshSessionRequest, RefreshSessionResponse};
 use tonic::{Request, Response, Status};
 use tracing::debug;
-use crate::grpc::{GetSessionRequest, GetSessionResponse, RefreshSessionRequest, RefreshSessionResponse};
 
 #[tonic::async_trait]
 impl SessionService for MyDatabaseService {
-    async fn get_session(
-        &self,
-        request: Request<GetSessionRequest>,
-    ) -> Result<Response<GetSessionResponse>, Status> {
+    async fn get_session(&self, request: Request<GetSessionRequest>) -> Result<Response<GetSessionResponse>, Status> {
         let req = request.into_inner();
         debug!("get_session: {:?}", req);
 
-        let session = self.db.session_repo.get_session(&req.session_id).await
+        let session = self
+            .db
+            .session_repo
+            .get_session(&req.session_id)
+            .await
             .map_err(|_| Status::not_found("Session not found"))?;
-        
+
         debug!("session: {:?}", session);
         Ok(Response::new(GetSessionResponse {
             session_id: session.id,
@@ -23,18 +24,23 @@ impl SessionService for MyDatabaseService {
         }))
     }
 
-    async fn refresh_session(&self, request: Request<RefreshSessionRequest>) -> Result<Response<RefreshSessionResponse>, Status> {
+    async fn refresh_session(
+        &self,
+        request: Request<RefreshSessionRequest>,
+    ) -> Result<Response<RefreshSessionResponse>, Status> {
         let req = request.into_inner();
         debug!("get_session: {:?}", req);
 
-        let session = self.db.session_repo.refresh_session(&req.session_id).await
+        let session = self
+            .db
+            .session_repo
+            .refresh_session(&req.session_id)
+            .await
             .map_err(|_| Status::not_found("Session not found"))?;
-        
+
         let valid = true;
-        
+
         debug!("session: {:?}", session);
-        Ok(Response::new(RefreshSessionResponse {
-            valid
-        }))
+        Ok(Response::new(RefreshSessionResponse { valid }))
     }
 }