Add support for form 3921

[mjsir911]

Spec can be found in publication 1120.

The only complicated bit I can see is if the foreign field is set then the address fields are treated differently.

Does this tool support union typed fields?

[darwinz]

Hi Marco, thanks for submitting an issue to add support for form 3921. And thanks for including a link to publication 1220 with the documentation for that form.

[darwinz]

Hi, @mjsir911 are you interested in contributing to the effort to add support for form 3921? If you would like to help with the development of this feature, let us know. Or if you can help with testing after the feature has been developed, that is also very helpful to ensure the feature works according to what is wanted.