The Invoice doesn't save contact historic data so if the contact is edited, it will appear that way in the invoice as well.
Only the item and quantity can be specified per item in an invoice and the rest of the information (tax, price) are
handled in the back end.
I did hack to be able to add multiple items to an invoice using jQuery. As a result, the style of the first item is
replicated whenever a new item is added. (no support for delete items).
I created a CompanySafeViewMixin that can be used with the Views and will ensure that each queryset takes the
company into account to prevent a user from seeing data from another user. This is just an experiment and may be broken.
The home page is pretty useless right now.
TODO
Get rid of the username and do auth with just email.