fix(templates): pages parse without markup errors, element IDs are unique

Rendered through every URL on libvirt's test driver, the pages had
duplicate IDs and markup browsers repaired silently:

- Each flavor modal's "Advanced" button toggled #flav-add-collapse, the
  first modal's section; every modal now has its own. The flavor and
  template copies of the custom tab's control IDs, and the template
  tab's unused images input, are gone.
- The VM page's action icons and the XML editors were styled by
  repeated IDs; they use classes.
- Modal forms opened inside modal-body and closed after modal-footer;
  they wrap both. Stray end tags and duplicate attributes are removed,
  paragraphs no longer hold modals or rows, table heads have a row, and
  the create page closes its row and column.
- html lang is the active language instead of "en".

A test walks every URL as a superuser and fails on a repeated ID. The
console page still has no doctype: its full-height layout relies on
quirks mode and needs its own check.

webvirtcloud/tests/test_unique_ids.py

@@ -0,0 +1,55 @@
+"""Every HTML page a superuser can open has unique element IDs: a repeated
+ID makes getElementById, labels and Bootstrap targets reach the first one
+only. Pages are rendered on libvirt's test driver."""
+
+from collections import Counter
+from unittest.mock import patch
+
+import libvirt
+from computes.models import Compute
+from django.contrib.auth import get_user_model
+from django.test import TestCase
+from django.urls import NoReverseMatch, URLPattern, URLResolver, get_resolver, reverse
+from instances.models import Flavor, Instance
+from lxml import html
+
+
+def named_urls(patterns, prefix="", keys=()):
+    for p in patterns:
+        if isinstance(p, URLResolver):
+            yield from named_urls(p.url_patterns, f"{prefix}{p.namespace}:" if p.namespace else prefix,
+                                  keys + tuple(p.pattern.regex.groupindex))
+        elif isinstance(p, URLPattern) and p.name:
+            yield prefix + p.name, keys + tuple(p.pattern.regex.groupindex)
+
+
+class UniqueIdTests(TestCase):
+    def test_no_page_repeats_an_id(self):
+        conn = libvirt.open("test:///default")
+        self.addCleanup(conn.close)
+        compute = Compute.objects.create(name="testdrv", hostname="localhost", login="", password="", type=4)
+        vm = Instance.objects.create(compute=compute, name="test", uuid=conn.lookupByName("test").UUIDString())
+        Flavor.objects.create(label="second", memory=512, vcpu=1, disk=10)  # the flavor modals repeat per flavor
+        self.client.force_login(get_user_model().objects.create_superuser("ids", "ids@example.com", "pw"))
+        self.client.raise_request_exception = False
+        values = {"pk": vm.id, "compute_id": compute.id, "pool": "default-pool", "arch": "i686", "machine": "pc"}
+        checked = []
+        with patch("vrtManager.connection.connection_manager.get_connection", return_value=conn), \
+             patch("vrtManager.connection.wvmConnect.get_machine_types", return_value=["pc"]), \
+             patch("vrtManager.connection.wvmConnect.get_nwfilters", return_value=[]), \
+             patch.object(libvirt.virConnect, "getMemoryStats", return_value={"total": 8 << 20, "free": 4 << 20, "buffers": 0, "cached": 0}), \
+             patch.object(libvirt.virConnect, "getCPUStats", return_value={"kernel": 1, "idle": 1, "user": 1, "iowait": 0}):
+            for name, keys in named_urls(get_resolver().url_patterns):
+                try:
+                    url = reverse(name, kwargs={k: values.get(k, 1) for k in keys})
+                except NoReverseMatch:
+                    continue
+                response = self.client.get(url)
+                if response.status_code != 200 or not response["Content-Type"].startswith("text/html"):
+                    continue
+                checked.append(name)
+                ids = Counter(html.fromstring(response.content).xpath("//@id"))
+                with self.subTest(page=name):
+                    self.assertEqual({i: n for i, n in ids.items() if n > 1}, {})
+        self.assertTrue({"index", "overview", "instances:instance", "nwfilter"} <= set(checked), checked)
+        self.assertIn("instances:create_instance", checked)