Integrate users and books

- new table userbook linking users and book
- moved rating to users book
- updated demo data and tests
- updated front to hide routes from non connected users

internal/db/init.go

@@ -20,6 +20,7 @@ func Initdb(databasePath string, demoDataPath string) *gorm.DB {
 	// Migrate the schema
 	db.AutoMigrate(&model.Book{})
 	db.AutoMigrate(&model.User{})
+	db.AutoMigrate(&model.UserBook{})
 	var book model.Book
 	queryResult := db.Limit(1).Find(&book)
 	if queryResult.RowsAffected == 0 && demoDataPath != "" {