**What**
- Catches unique constraints on customer_id, is_default_billing/is_default_shipping and reformats
- Adds an step to create and update of addresses that unsets the previous default shipping/billing address if necessary.
- This creates a behavior in the API where you can always set an address to be default and it will automatically unset the previous one for you.
**What**
- GET /admin/customers/:id/addresses
- POST /admin/customers/:id/addresses
- POST /admin/customers/:id/addresses/:address_id
- DELETE /admin/customers/:id/addresses/:address_id
**What**
```
POST /admin/customer-groups
POST /admin/customer-groups/:id
GET /admin/customer-groups/:id
DELETE /admin/customer-groups/:id
```
- Workflows