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/model/user.go

@@ -4,6 +4,7 @@ import "gorm.io/gorm"
 
 type User struct {
 	gorm.Model
-	Name     string `gorm:"index;uniqueIndex"`
-	Password string
+	Name      string `gorm:"index;uniqueIndex"`
+	Password  string
+	UserBooks []UserBook
 }