Add initial project structure with core functionality for book and stationery uploads

- Created main application entry point in `main.go`.
- Added configuration management in `config/config.go` and tests in `config/config_test.go`.
- Implemented handlers for book and stationery uploads in `handlers/book.go` and `handlers/stationery.go`, including validation logic.
- Established database connection and services in `services/database.go` and `services/book_service.go`.
- Defined models for books and stationery in `models/book.go` and `models/stationery.go`.
- Set up Firebase integration for image uploads in `services/firebase.go`.
- Created migration scripts for database schema in `migrations/001_create_tables.sql` and subsequent updates.
- Added CORS and error handling middleware.
- Included comprehensive tests for handlers, services, and utilities.
- Documented API endpoints and usage in `README.md` and migration instructions in `migrations/README.md`.
- Introduced `.gitignore` to exclude unnecessary files and directories.
- Added Go module support with `go.mod` and `go.sum` files.
- Implemented utility functions for slug generation and validation in `utils/slug.go` and `utils/validation.go`.

utils/slug.go

@@ -0,0 +1,87 @@
+package utils
+
+import (
+	"regexp"
+	"strings"
+	"unicode"
+)
+
+// GenerateSlug converts a string to a URL-friendly slug
+// Converts to lowercase, replaces spaces with hyphens, removes special characters
+func GenerateSlug(text string) string {
+	if text == "" {
+		return ""
+	}
+
+	// Convert to lowercase
+	slug := strings.ToLower(text)
+
+	// Replace spaces and underscores with hyphens
+	slug = strings.ReplaceAll(slug, " ", "-")
+	slug = strings.ReplaceAll(slug, "_", "-")
+
+	// Remove all non-alphanumeric characters except hyphens
+	reg := regexp.MustCompile(`[^a-z0-9-]`)
+	slug = reg.ReplaceAllString(slug, "")
+
+	// Remove multiple consecutive hyphens
+	reg = regexp.MustCompile(`-+`)
+	slug = reg.ReplaceAllString(slug, "-")
+
+	// Remove leading and trailing hyphens
+	slug = strings.Trim(slug, "-")
+
+	// If empty after processing, return a default
+	if slug == "" {
+		slug = "item"
+	}
+
+	return slug
+}
+
+// IsValidSlug checks if a string is a valid slug format
+func IsValidSlug(slug string) bool {
+	if slug == "" {
+		return false
+	}
+
+	// Check if it contains only lowercase letters, numbers, and hyphens
+	reg := regexp.MustCompile(`^[a-z0-9-]+$`)
+	if !reg.MatchString(slug) {
+		return false
+	}
+
+	// Check it doesn't start or end with hyphen
+	if strings.HasPrefix(slug, "-") || strings.HasSuffix(slug, "-") {
+		return false
+	}
+
+	// Check it doesn't have consecutive hyphens
+	if strings.Contains(slug, "--") {
+		return false
+	}
+
+	return true
+}
+
+// CleanString removes leading/trailing whitespace and normalizes spaces
+func CleanString(s string) string {
+	// Trim whitespace
+	s = strings.TrimSpace(s)
+
+	// Replace multiple spaces with single space
+	reg := regexp.MustCompile(`\s+`)
+	s = reg.ReplaceAllString(s, " ")
+
+	return s
+}
+
+// ContainsOnlyLetters checks if a string contains only letters (and spaces)
+func ContainsOnlyLetters(s string) bool {
+	for _, r := range s {
+		if !unicode.IsLetter(r) && !unicode.IsSpace(r) {
+			return false
+		}
+	}
+	return true
+}