Delete a post.

    Ensures that the post exists and that the logged in user is the
    author of the post.

def delete(id):
    """Delete a post.

    Ensures that the post exists and that the logged in user is the
    author of the post.
    """
    post = get_post(id)
    db.session.delete(post)
    db.session.commit()
    return redirect(url_for("blog.index"))