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

world-service/README.md

@@ -0,0 +1,95 @@
+# World Service
+
+The World Service manages the game world state and character interactions in the MMORPG server architecture.
+
+## Overview
+
+The World Service is responsible for:
+- Managing character positions and movement
+- Handling map changes
+- Processing character interactions
+- Managing NPCs, monsters, and objects
+- Handling combat and skills
+
+## Architecture
+
+The service is built using the following components:
+
+- **gRPC Server**: Exposes world management endpoints
+- **World State Manager**: Maintains the current state of the game world
+- **Map Manager**: Handles map data and transitions
+- **Entity Manager**: Manages characters, NPCs, and monsters
+
+## Service Endpoints
+
+The World Service exposes the following gRPC endpoints:
+
+### GetCharacter
+Retrieves a character's world state.
+
+```protobuf
+rpc GetCharacter(CharacterRequest) returns (CharacterResponse);
+```
+
+### ChangeMap
+Handles a character changing maps.
+
+```protobuf
+rpc ChangeMap(ChangeMapRequest) returns (ChangeMapResponse);
+```
+
+### MoveCharacter
+Updates a character's position.
+
+```protobuf
+rpc MoveCharacter(CharacterMoveRequest) returns (CharacterMoveResponse);
+```
+
+### GetTargetHp
+Retrieves an object's current HP.
+
+```protobuf
+rpc GetTargetHp(ObjectHpRequest) returns (ObjectHpResponse);
+```
+
+## World Data Structure
+
+The world consists of:
+
+- **Maps**: Different areas with unique IDs
+- **Spawn Points**: Locations where characters can appear
+- **NPCs**: Non-player characters with fixed positions
+- **Monsters**: Hostile entities that can move and attack
+- **Objects**: Interactive items in the world
+
+## Configuration
+
+The service can be configured using environment variables:
+
+- `LISTEN_ADDR`: The address to listen on (default: "0.0.0.0")
+- `SERVICE_PORT`: The port to listen on (default: "50054")
+- `LOG_LEVEL`: Logging level (default: "info")
+
+## Running the Service
+
+### Local Development
+
+```bash
+cargo run
+```
+
+### Docker
+
+```bash
+docker build -t world-service .
+docker run -p 50054:50054 world-service
+```
+
+## Integration with External Systems
+
+The World Service integrates with:
+
+- **Database Service**: For retrieving and storing world state
+- **Auth Service**: For user authentication and authorization
+- **Character Service**: For character data
+- **Packet Service**: For handling client requests related to the world