add tests, improve tests

[simonLeary42]

While writing tests, I discovered that allocation/views.py likes to do message.error followed by HttpResponseRedirect, and the test cases only check response.status_code, which is either 200 or 301, depending on if follow was specified. I added a new utility to check both response.status_code and check for error messages.

• tests tweaked to check for error messages:
  • test_allocationchangedetailview_post_deny
  • test_allocationchangeview_post_extension
  • test_allocationchangeview_post_no_change
  • test_allocationcreateview_post_zeroquantity
  • test_centersummary_renders
• other test changes:
  • test_allocationchangedetailview_access renamed to test_allocationchangedetailview_access_granted to differentiate it from test_allocationchangedetailview_access_denied
  • test_allocationchangeview_post_extension:
    • created local copy of self.post_data to prevent this test from messing up other tests with its specific post_data
    • added more specific assertion
  • AllocationViewBaseTest:
    • added type hints to object attributes
    • added end_date to cls.allocation so that the new end date could be calculated after approving an end date extension
    • made cls.quota_attribute.allocation_attribute_type changeable
  • test_allocationchangedetailview_post_deny: tweaked to use status.name (string) instead of status_id (object primary key), more intuitive
• new tests added:
  • test_allocationchangedetailview_access_denied
  • test_allocationchangedetailview_post_approve_end_date_extension
  • test_allocationchangedetailview_post_approve_attribute_change
  • test_allocationchangedetailview_post_update_end_date_extension
  • test_allocationchangeview_post_attribute_change

Also added documentation to explain the diffrence between AllocationChangeView and AllocationChangeDetailView, and their get_allocation_attributes_to_change, which share the same name but do different things.

[simonLeary42]

CI failure is fixed by #847