Function options 

pub fn options<F, Args>(f: F) -> RouterItemBuilder
where
    for<'r, 'r> F: FnTrait<Args> + 'r + FnTrait<Args::Output<'r>>,
    for<'r> Args: FromRequest + 'r,
    for<'r> <F as FnTrait<Args::Output<'r>>>::Output: Responder,