如何在elm中使用form配置http请求

type Msg
    = FormSubmitted (Result Http.Error String)

type alias Model =
    { formResult : Result Http.Error String
    , ...
    }

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
    case msg of
        FormSubmitted result ->
            ( { model | formResult = result }
            , Http.send handleFormResponse <| Http.post "https://example.com/api/endpoint" formEncoder
            )
        ...

formEncoder : Http.BodyEncoder
formEncoder =
    Http.formData [ ( "Content-Type", "application/x-www-form-urlencoded" ) ]

handleFormResponse : Result Http.Error (Http.Response String) -> Msg
handleFormResponse result =
    case result of
        Ok response ->
            case response.statusCode of
                200 ->
                    FormSubmitted (Ok response.body)

                _ ->
                    FormSubmitted (Err "Request failed")

        Err error ->
            FormSubmitted (Err (Http.errorToString error))

view : Model -> Html Msg
view model =
    ...
    form [ onSubmit FormSubmitted ]
        [ input [ type_ "text", name "username" ] []
        , input [ type_ "password", name "password" ] []
        , button [ type_ "submit" ] [ text "Submit" ]
        ]
    ...