restructure application, add get endpoint

internal/application/services.go

@@ -0,0 +1,19 @@
+package application
+
+import (
+	"vegan-barcode/internal/models"
+)
+
+func (a *Application) GetClaims(system string, barcode string) (*models.ProductClaims, error) {
+	id, err := a.db.FindProductIDByBarcode(system, barcode)
+	if err != nil {
+		return nil, err
+	}
+
+	claims, err := a.db.FindClaimsByProductID(id)
+	if err != nil {
+		return nil, err
+	}
+
+	return &models.ProductClaims{Id: id, Claims: claims}, nil
+}