Function seed_datepicker::update

pub fn update<Ms: 'static, T: HasDateConstraints + Default + Clone>(
    msg: Msg, 
    model: &mut Model<T>, 
    orders: &mut impl Orders<Ms>, 
    on_change: Ms, 
    to_msg: impl FnOnce(Msg) -> Ms + Clone + 'static
)

update describes how to handle each Msg.