UI Design - Validation for Sole Proprietorship Registration

- A sole proprietorship may not be the owner of another sole proprietorship
- In a case where a sole proprietor wants to register a secondary sole proprietorship they must still register using their name as the proprietor, rather than their existing sole proprietorship business name
- A sole proprietorship may also not list a start date more than 10 days in the future
- RAID #796 noted we are not tackling larger model changes now

TASK:
- [ ] Create design for validation preventing a sole proprietorship from listing another sole proprietorship as the proprietor.
- [ ] Create design for validation preventing a sole proprietorship from listing a start date more than 10 days in the future