testing update + docs

backend/handlers/auth/auth_test.go

@@ -1,6 +1,25 @@
 //go:build test
 // +build test
 
+// Package auth contains tests for authentication and verification endpoints.
+//
+// Test Coverage:
+//   - RegisterHandler: POST /api/register - User registration
+//     * Validates: required fields, email format, UK phone, age >= 16, duplicate email
+//   - LoginHandler: POST /api/login - User login
+//     * Validates credentials, returns JWT token
+//   - RefreshTokenHandler: POST /api/refresh-token - Refresh JWT token
+//   - GenerateVerificationCodeHandler: POST /api/verify/generate - Send verification code
+//     * Returns success even for non-existent emails (security)
+//   - VerifyCodeHandler: POST /api/verify/check - Verify code and update user role
+//     * Validates: correct code, not expired, not already used
+//     * Updates user role from unverified_email to verified_email on success
+//
+// Validation: Comprehensive tests for invalid inputs (bad email, bad phone, underage, etc.)
+package auth
+//go:build test
+// +build test
+
 package auth
 
 import (