pub fn map_async_with_description<'a, Projection, Output, NewType, Args, Descr>(
description: Descr,
proj: Projection,
) -> Handler<'a, Output, Descr>where
Projection: Injectable<NewType, Args> + Send + Sync + 'a,
Output: 'a,
Descr: HandlerDescription,
NewType: Send + Sync + 'static,Expand description
map_async with a custom description.