Externalize configuration values

Configuration files should not contain hardcoded values for usernames, credentials, hostnames, or environment-specific settings. Instead, use environment variables, templated values, or dynamic references that can adapt to different deployment contexts.

This approach improves:

• Security: Prevents credentials from being checked into source control
• Portability: Allows configurations to work across different environments
• Collaboration: Makes it easier for teams to work on the same codebase without conflicts

For Docker and CI/CD configurations:

# In docker-compose.yml
- DATABASE_URL: "postgresql://postgres:password@db:5432/inboxzero?schema=public"
+ DATABASE_URL: ${DATABASE_URL:-postgresql://${POSTGRES_USER:-postgres}:${POSTGRES_PASSWORD}@db:5432/${POSTGRES_DB:-inboxzero}?schema=public}

# In GitHub workflows
- DOCKER_USERNAME: "elie222"
+ DOCKER_USERNAME: "$"

# In Docker images
- image: ghcr.io/elie222/inbox-zero:latest
+ image: ghcr.io/${ORGANIZATION:-$USER}/inbox-zero:latest

For sensitive values, consider using secrets management systems for production environments. For local development, provide .env.example files as templates that developers can copy to create their own .env files, which should be excluded from version control.