Non-generic to generic Result MapFailure method

[paulirwin]

There is a MapFailure method on Result<T>, but not on Result. I just encountered a situation where it makes sense to do so.

This method should be added to the non-generic Result class (note the lack of <T> compared to the generic Result<T> version):

/// <summary>
/// Maps the failure result to another type.
/// </summary>
/// <typeparam name="TOther">The type to map to.</typeparam>
/// <returns>A <see cref="Result{TOther}"/>.</returns>
/// <exception cref="InvalidOperationException">Thrown if the result type is not known.</exception>
public Result<TOther> MapFailure<TOther>() =>
    this switch
    {
        SuccessResult => throw new InvalidOperationException("Cannot map failure on success result"),
        ValidationFailedResult validationFailed => Result<TOther>.ValidationFailed(validationFailed.Errors),
        UnauthorizedResult unauthorized => Result<TOther>.Unauthorized(unauthorized.Message),
        PreconditionFailedResult preconditionFailed => Result<TOther>.PreconditionFailed(preconditionFailed.Reason, preconditionFailed.Message),
        _ => throw new InvalidOperationException("Unknown result type")