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/redis_cache.rs

@@ -1,16 +1,12 @@
 use async_trait::async_trait;
 use deadpool_redis::{Config, Pool, Runtime};
-use redis::{AsyncCommands, Commands, RedisError};
+use redis::{AsyncCommands, RedisError};
 use serde::{Deserialize, Serialize};
 
 #[async_trait]
 pub trait Cache {
-    async fn set<T: Serialize + Send + Sync>(
-        &self,
-        key: &String,
-        value: &T,
-        ttl: u64,
-    ) -> Result<(), redis::RedisError>;
+    async fn set<T: Serialize + Send + Sync>(&self, key: &String, value: &T, ttl: u64)
+        -> Result<(), redis::RedisError>;
 
     async fn update<T: Serialize + Send + Sync>(
         &self,