Limited ahd experimental for now; waiting for generics in operator overloading to be actually useful.
Returns the Err back when IsErr; Ok(map(Unwrap())) when IsOk.// session will be Err if the user is Err; Ok of a session for the user when Ok.
Res<Session> session = TryGetUser.Map(user => NewSession(user.Secrets));
public static Res<T> operator /(
Res<T> result,
Func<T, T> map
)