Fix "Cookbook" -> "Using a request object"

[s1beria21]

Last snippet has

data["user_id"] = request.user.id

but Post model has

author = relationship("User")
author_id = mapped_column(Integer, ForeignKey("user.id"), index=True)

I think should change from user_id to author_id

[aminalaee]

Indeed, you are right. Feel free to create a PR for that.