* constraint: no Organisation as source_section
* constraint: fixup empty price check
* constraint: destination_section is not required

for accounting less subscription

* contraint: source_section is not required on Open Sale Order
  Needed for accounting less Open Order.
* constraint: source_section is not required on Sale Packing List
* constraint: no Organisation as destination / destination_section

This work must be done later

* init preferences in test
* test: wip accounting scenario
* test:  slapos_subscription_request is installed again

* trigger validation as soon as a Subscription Request is submitted
* decrease slapos_subscription_request_validate_submitted alarm periodicity
* create Subscription Request as soon as a Compute Node is validated
* create Subscription Request as soon as Instance Tree is validated

* test Compute Node subscription creation
* logout test

Let's automate everything for now