Add position for book in collection

internal/model/collection.go

@@ -7,5 +7,5 @@ type Collection struct {
 	Name   string
 	User   User
 	UserID uint
-	Books  []Book `gorm:"many2many:collection_books;"`
+	Items  []CollectionItem
 }

internal/model/collectionitem.go

@@ -0,0 +1,11 @@
+package model
+
+import "gorm.io/gorm"
+
+type CollectionItem struct {
+	gorm.Model
+	CollectionID uint
+	Position     uint
+	Book         Book
+	BookID       uint
+}