## Overview of Application Layers

This project follows a layered architecture to ensure separation of concerns, maintainability, and scalability. Below is an overview of the different layers and their responsibilities:

### 1. **Controller Layer**
   - **Purpose**: Handles HTTP requests and responses.
   - **Responsibilities**:
     - Accept input from clients (e.g., REST API calls).
     - Delegate processing to the service layer.
     - Return appropriate responses (e.g., JSON, HTTP status codes).
   - **Example**: `UserController` processes user-related API requests.

### 2. **Service Layer**
   - **Purpose**: Encapsulates business logic and application workflows.
   - **Responsibilities**:
     - Implements core business rules.
     - Orchestrates calls to adapters and other services.
     - Ensures data integrity and validation.
   - **Example**: `UserService` handles user-related operations such as fetching user details or loading default users.

### 3. **Adapter Layer**
   - **Purpose**: Acts as a bridge between the application and external systems or dependencies.
   - **Responsibilities**:
     - Abstracts interactions with external APIs, databases, or other services.
     - Translates data formats between the application and external systems.
   - **Example**: `UserAdapter` fetches user details from a database or external API.

### 4. **Domain Layer**
   - **Purpose**: Represents the core business entities and logic.
   - **Responsibilities**:
     - Defines domain models and their behavior.
     - Contains business rules that are independent of external systems.
   - **Example**: `CustomUserDetails` represents a user in the system.

### 5. **Infrastructure Layer**
   - **Purpose**: Provides technical implementations for external dependencies.
   - **Responsibilities**:
     - Implements adapters for databases, APIs, or other external systems.
     - Handles configuration and low-level technical details.
   - **Example**: A database repository or an API client implementation.

### Layer Interaction
- **Controllers** interact with **services** to process requests.
- **Services** use **adapters** to interact with external systems.
- **Adapters** handle the technical details of communication with external systems.
- **Domain models** are used across all layers to represent core business entities.

### Benefits of Layered Architecture
- **Separation of Concerns**: Each layer has a distinct responsibility, making the code easier to understand and maintain.
- **Scalability**: Layers can be modified or replaced independently.
- **Testability**: Each layer can be tested in isolation.

This architecture ensures that the application is modular, maintainable, and easy to extend.