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`.

middleware/error_handler_test.go

@@ -0,0 +1,63 @@
+package middleware
+
+import (
+	"errors"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gofiber/fiber/v2"
+)
+
+func TestErrorHandler(t *testing.T) {
+	app := fiber.New()
+	app.Use(ErrorHandler)
+
+	app.Get("/error", func(c *fiber.Ctx) error {
+		return fiber.NewError(fiber.StatusBadRequest, "Bad Request")
+	})
+
+	app.Get("/panic", func(c *fiber.Ctx) error {
+		return errors.New("some error")
+	})
+
+	// Test Fiber error
+	req := httptest.NewRequest("GET", "/error", nil)
+	resp, err := app.Test(req)
+	if err != nil {
+		t.Fatalf("Test request failed: %v", err)
+	}
+
+	if resp.StatusCode != fiber.StatusBadRequest {
+		t.Errorf("Expected status %d, got %d", fiber.StatusBadRequest, resp.StatusCode)
+	}
+
+	// Test generic error
+	req = httptest.NewRequest("GET", "/panic", nil)
+	resp, err = app.Test(req)
+	if err != nil {
+		t.Fatalf("Test request failed: %v", err)
+	}
+
+	if resp.StatusCode != fiber.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", fiber.StatusInternalServerError, resp.StatusCode)
+	}
+}
+
+func TestRecoverHandler(t *testing.T) {
+	app := fiber.New()
+	app.Use(RecoverHandler())
+
+	app.Get("/panic", func(c *fiber.Ctx) error {
+		panic("test panic")
+	})
+
+	req := httptest.NewRequest("GET", "/panic", nil)
+	resp, err := app.Test(req)
+	if err != nil {
+		t.Fatalf("Test request failed: %v", err)
+	}
+
+	if resp.StatusCode != fiber.StatusInternalServerError {
+		t.Errorf("Expected status %d, got %d", fiber.StatusInternalServerError, resp.StatusCode)
+	}
+}