So:
'billing_contact_email_address' becomes 'billing_contact_email_addresses'
AND
'billing_contact_name' becomes 'billing_contact_names'
This is to signify that each of those fields can contain numerous
items
The fields are:
Purchase order number - string field
Billing contact name - text field to acommodate possible multiple
contacts
Billing contact email address - text field to acommodate possible
multiple contacts
Billing reference - string field
All these fields are nullable. Notify platform admins will be
able to check and edit those values in Service Settings
section in Notify interface.
This will help make billing tasks and reports simpler.
Similar fields will also be added to Organisation model and
db table.
