- Validate domain name format: letters, numbers, dots, hyphens only
- Must have at least one dot (TLD required)
- Cannot start/end with dot or hyphen
- Label length 1-63 characters
- Return ValidationError with descriptive message
- Added gin-gonic v1.10.0 dependency
- Refactored router.go: clean route groups with middleware chains
- Refactored all handlers to use gin.Context instead of http.ResponseWriter/*http.Request
- Simplified response helpers (JSON, Error, Success, Created, NoContent)
- Clean auth middleware using Gin's c.Set() for context
- Cleaner route definitions with path parameters (e.g., /domains/:name/users/:id)
- Admin routes moved to /api/admin group with RequireAdmin middleware
