func ShowEditPostFormError(w http.ResponseWriter, params *ess.Command, err error) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
NewHTMLDocument("Edit Post",
EditPostForm.
Fill(params, err).
Action("/posts/"+params.AggregateId()+"/edit").
Param("id", params.AggregateId()).
Param("username", params.Get("username").String()).
ToHTML("Edit post"),
).WriteHTML(w, "", " ")
}
func PostFromCommand(params *ess.Command) ess.Aggregate {
return NewPost(params.AggregateId())
}