Banking.ts authorization failure returns 404 instead of 403

[beejones]

When authentication passes but validation fails, we need to return 403 and not 404.
This is an example of what is in the code on the endpoints
if (!validateUserId(userId)) {
return {
statusCode: 404,
};
}
The status code must be 403.

[ross-p-smith]

Hi @beejones - if you create a PR - I'll happily review.