ci: test IPv6 for CIDR resources (#10168)

Docker for Mac finally supports IPv6 in general availability. It's time
to add IPv6 to our suite of integration tests.

The thinking behind this PR is try and not slow down CI much, if at all,
by testing IPv6 side-by-side with the existing IPv4 tests.

More comprehensive testing is being developed in #10131 that will test
things like IPv4-in-6 relaying, client / gateway IP stack mismatches,
and so forth.

elixir/apps/domain/priv/repo/seeds.exs

@@ -1001,6 +1001,19 @@ defmodule Domain.Repo.Seeds do
         admin_subject
       )
 
+    {:ok, ipv6_resource} =
+      Resources.create_resource(
+        %{
+          type: :cidr,
+          name: "MyCorp Network (IPv6)",
+          address: "172:20:0::1/64",
+          address_description: "172:20:0::1/64",
+          connections: [%{gateway_group_id: gateway_group.id}],
+          filters: []
+        },
+        admin_subject
+      )
+
     {:ok, dns_httpbin_resource} =
       Resources.create_resource(
         %{
@@ -1044,6 +1057,7 @@ defmodule Domain.Repo.Seeds do
     IO.puts("  #{example_dns.address} - DNS - gateways: #{gateway_name}")
     IO.puts("  #{ip_resource.address} - IP - gateways: #{gateway_name}")
     IO.puts("  #{cidr_resource.address} - CIDR - gateways: #{gateway_name}")
+    IO.puts("  #{ipv6_resource.address} - CIDR - gateways: #{gateway_name}")
     IO.puts("  #{dns_httpbin_resource.address} - DNS - gateways: #{gateway_name}")
     IO.puts("  #{search_domain_resource.address} - DNS - gateways: #{gateway_name}")
     IO.puts("")
@@ -1128,6 +1142,16 @@ defmodule Domain.Repo.Seeds do
         admin_subject
       )
 
+    {:ok, _} =
+      Policies.create_policy(
+        %{
+          name: "All Access To Network",
+          actor_group_id: synced_group.id,
+          resource_id: ipv6_resource.id
+        },
+        admin_subject
+      )
+
     {:ok, _} =
       Policies.create_policy(
         %{