I'll help you add documentation by creating a README.md file and adding some package-level documentation. Let's start with the main README:

```markdown:README.md
# BYOM Gateway

BYOM Gateway is a Go-based service that manages user-host associations with a secure REST API.

## Features

- RESTful API for user-host management
- SQLite database with WAL mode for data persistence
- Secure by default with comprehensive security middleware
- Structured logging and request tracing
- Configuration via YAML
- Basic authentication support

## Prerequisites

- Go 1.19 or higher
- SQLite 3

## Quick Start

1. Clone the repository:
```bash
git clone git.linuxforward.com/byom/byom-core-gateway
cd byom-gateway
```

2. Copy the sample config:
```bash
cp config.sample.yaml config.yaml
```

3. Build and run:
```bash
go build
./byom-gateway
```

## Configuration

Configuration is managed through a YAML file. Example configuration:

```yaml
server:
  port: "8080"
  tls:
    enabled: false
    cert: ""
    key: ""

database:
  file: "./data/dev.db"
  log_mode: true
  max_open_conns: 10
  max_idle_conns: 5
  conn_max_lifetime: 3600
  pragma:
    - "journal_mode=WAL"
    - "busy_timeout=5000"
    - "foreign_keys=ON"

basic_auth:
  username: "admin"
  password: "your_secure_password"
```

## API Documentation

### User-Host Management

#### Get User Host
```http
GET /api/v1/user-host?email=user@example.com
```

Response:
```json
{
    "email": "user@example.com",
    "host": "host.example.com"
}
```

#### Add User Host
```http
POST /api/v1/user-host
```

Request body:
```json
{
    "email": "user@example.com",
    "host": "host.example.com"
}
```

## Security

The service implements several security measures:

- CORS protection
- Security headers (HSTS, CSP, etc.)
- Request sanitization
- Basic authentication
- TLS support
- Request rate limiting

## Development

### Project Structure

```
.
├── app/            # Application initialization and setup
├── config/         # Configuration handling
├── errors/         # Custom error types
├── handlers/       # HTTP request handlers
├── logger/         # Logging configuration
├── middleware/     # HTTP middleware
├── store/          # Database operations
└── main.go         # Application entry point
```

### Adding New Features

1. Add new models to `store/`
2. Create handlers in `handlers/`
3. Register routes in `app/app.go`
4. Update configuration if needed
5. Add tests

## License

[License details here]