Web App: UI for A4a

[smiththay]

• [ ] Define the A4a model with all necessary properties
• [ ] Update all mappers and form fields
• [ ] Validate fields with Regex, range, custom validation, etc.
• [ ] Add form to form contract
• [ ] Update A4a UI to match NACC documentation.
• [ ] Modify enable/disable behavior and implement on UI
• [ ] Insure form matches NACC documentation with correct UI, logic, validation, behavior and ensure data is saving correctly

View Docs: https://github.com/naccdata/uniform-data-set/tree/main/forms/uds/a4a