fix(instances): a template is not power-cycled on, and deleted only by superusers and staff owners

Power cycle force-stopped and started a template, which power on refuses.
A non-staff owner with is_delete could delete a template that the
template rule otherwise leaves to superusers and staff owners;
get_instance(perm_type="delete") now refuses it, and the page offers
Destroy by the same rule.

instances/test_template_rules.py

@@ -0,0 +1,64 @@
+"""
+A template is not started (power on or power cycle, web or API) and is
+changed or deleted only by superusers and staff owners.
+"""
+from unittest.mock import patch
+
+from django.contrib.auth import get_user_model
+from django.test import TestCase
+from django.urls import reverse
+from rest_framework.test import APIClient
+
+from accounts.models import UserInstance
+from computes.models import Compute
+from instances.models import Instance
+
+
+class TemplateRulesTestCase(TestCase):
+    def setUp(self):
+        compute = Compute.objects.create(name="tpl-c", hostname="192.0.2.5", login="root", password="", type=1)
+        self.template = Instance.objects.create(
+            compute=compute, name="tpl-vm", uuid="ffffffff-0000-1111-2222-333333333333", is_template=True
+        )
+        self.owner = get_user_model().objects.create_user("tpl_owner", password="x")
+        UserInstance.objects.create(instance=self.template, user=self.owner, is_delete=True)
+        self.staff = get_user_model().objects.create_user("tpl_staff", password="x", is_staff=True)
+        UserInstance.objects.create(instance=self.template, user=self.staff, is_delete=True)
+
+    def test_power_cycle_does_not_start_a_template(self):
+        api = APIClient()
+        api.force_login(self.owner)
+        self.client.force_login(self.owner)
+        for post in (
+            lambda: self.client.post(reverse("instances:powercycle", args=[self.template.id])),
+            lambda: api.post(reverse("compute-instance-powercycle", args=[self.template.compute_id, self.template.id])),
+        ):
+            with patch("instances.models.wvmInstance") as wvm:
+                post()
+            self.assertFalse(wvm.return_value.start.called)
+            self.assertFalse(wvm.return_value.force_shutdown.called)
+
+    def test_only_staff_owners_delete_a_template(self):
+        self.client.force_login(self.owner)
+        with patch("instances.models.wvmInstance") as wvm:
+            response = self.client.post(reverse("instances:destroy", args=[self.template.id]))
+        self.assertEqual(response.status_code, 403)
+        self.assertFalse(wvm.return_value.delete.called)
+
+        self.client.force_login(self.staff)
+        with patch("instances.models.wvmInstance") as wvm:
+            wvm.return_value.instance.isActive.return_value = False
+            self.client.post(reverse("instances:destroy", args=[self.template.id]))
+        self.assertTrue(wvm.return_value.delete.called)
+
+    def test_the_destroy_confirmation_page_offers_the_form_to_who_may_delete(self):
+        url = reverse("instances:destroy", args=[self.template.id])
+        superuser = get_user_model().objects.create_superuser("tpl_root", "r@example.com", "x")
+        for user, status, form in ((superuser, 200, True), (self.staff, 200, True), (self.owner, 403, False)):
+            with self.subTest(user=user.username):
+                self.client.force_login(user)
+                with patch("instances.models.wvmInstance") as wvm:
+                    wvm.return_value.get_status.return_value = 5
+                    response = self.client.get(url)
+                self.assertEqual(response.status_code, status)
+                self.assertEqual('id="delete_form"' in response.content.decode(), form)