Extend ErrorResponse/ErrorType with enumerated errorCode about plaid-java

[phoenixy1]

Thanks for the feedback! As you allude to, this is technically doable, but would be a bit of a project to do in a maintainable way given that we add error codes pretty frequently without versioning the API. And I wonder if it might lead to a false sense of security since, as mentioned, this is a part of the API contract that we consider to be flexible (with the exception that we won't change an existing error code that we expect developers to handle during runtime).

If other folks would like to see this, would definitely appreciate votes/comments to get a gauge of the popularity of the request.

[phoenixy1]

Closing the issue as we are not currently planning to do this.