Follow what the live server does with tenants and domains

A run on the production server with throwaway tenants, a role, lists and a
domain, all removed, found three things the source reading had not:

- Something in a tenant has to be on a domain in that tenant (a list in a
  tenant on an unassigned domain is invalidForeignKey), while something in
  no tenant may be on a tenant's domain. The account panel's tenant choice
  offered every tenant; it offers only the domain's now, and a new account
  starts in the tenant of the domain it is made on. The domain list reads
  memberTenantId for it.
- A domain created in a tenant puts its DKIM keys there too, and they keep
  the tenant from being deleted. They are counted with the rest, so Delete
  is not offered while any remain.
- Stalwart lets a domain leave a tenant while the tenant still has accounts
  on it, stranding them. The panel asks first and refuses while any are
  there.

The refusal to delete a tenant that holds anything was confirmed, as were
tenant create, quota pointers, logo and rename. The mock follows the domain
rule, filters DKIM keys by tenant, and KNOWN-ISSUES records the run.

The non-Enterprise notice is now just "Tenants are a Stalwart Enterprise
feature." Two sentences were reworded and one plural added, in all nine
catalogues, and the old sentences are gone.

server/src/mock/directory.test.ts

@@ -286,3 +286,17 @@ test("a tenant administrator cannot move anything into a tenant", () => {
   assert.equal(r.notUpdated?.d4?.type, "invalidPatch");
   assert.match(r.notUpdated!.d4!.description, /memberTenantId/);
 });
+
+test("something in a tenant has to be on a domain in it, and something in none may be anywhere", () => {
+  const dir = make("admin");
+  const outside = dir.handlers["x:MailingList/set"]!({ create: { n: { name: "stray", domainId: "d1", memberTenantId: "t1" } } }) as { notCreated?: Record<string, { type: string; objectId: { object: string } }> };
+  assert.equal(outside.notCreated?.n?.type, "invalidForeignKey");
+  assert.equal(outside.notCreated!.n!.objectId.object, "Domain");
+  const inside = dir.handlers["x:MailingList/set"]!({ create: { n: { name: "team", domainId: "d3", memberTenantId: "t1" } } }) as { created?: Record<string, { id: string }> };
+  assert.ok(inside.created?.n?.id);
+  const none = dir.handlers["x:MailingList/set"]!({ create: { n: { name: "open", domainId: "d3" } } }) as { created?: Record<string, { id: string }> };
+  assert.ok(none.created?.n?.id);
+  const [someone] = (dir.handlers["x:Account/query"]!({ filter: { "@type": "User", domainId: "d1" } }) as { ids: string[] }).ids;
+  const move = dir.handlers["x:Account/set"]!({ update: { [someone!]: { memberTenantId: "t1" } } }) as { notUpdated?: Record<string, { type: string }> };
+  assert.equal(move.notUpdated?.[someone!]?.type, "invalidForeignKey");
+});