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

packet-service/src/handlers/auth.rs

@@ -133,10 +133,7 @@ pub(crate) async fn handle_login_req(
     connection_id: String,
     addr: SocketAddr,
 ) -> Result<(), Box<dyn Error + Send + Sync>> {
-    debug!(
-        "decoding packet payload of size {}",
-        packet.payload.as_slice().len()
-    );
+    debug!("decoding packet payload of size {}", packet.payload.as_slice().len());
     let data = CliLoginTokenReq::decode(packet.payload.as_slice())?;
     debug!("{:?}", data);
 
@@ -175,9 +172,7 @@ pub(crate) async fn handle_login_req(
                                     "name" => {
                                         server_name = value;
                                     }
-                                    "tags" => {
-
-                                    }
+                                    "tags" => {}
                                     _ => {}
                                 }
                             }