Minimal api allows to describe response types

[uabarahona]

Description

Right now, it is possible to add description to response types by using WithOpenApi:

.WithOpenApi(options =>
{
    options.Responses["400"].Description = "Describe what would cause this.";
    return options;
});

though I think a more concise way of doing it seems to be missing here, like on MVC:

✏️ Minimal APIs are looking awesome!!

[BrennanConroy]

Possible dupe of #39927

[rafikiassumani-msft]

Triage: Closing as a dupe.