feat: allow disabling registration

lib/accounts/user/validations/registration_enabled.ex

@@ -0,0 +1,27 @@
+defmodule Mv.Accounts.User.Validations.RegistrationEnabled do
+  @moduledoc """
+  Validation that blocks direct registration (register_with_password) when
+  registration is disabled in global settings. Used so that even direct API/form
+  submissions cannot register when the setting is off.
+  """
+  use Ash.Resource.Validation
+
+  alias Mv.Membership
+
+  @impl true
+  def init(opts), do: {:ok, opts}
+
+  @impl true
+  def validate(_changeset, _opts, _context) do
+    case Membership.get_settings() do
+      {:ok, %{registration_enabled: true}} ->
+        :ok
+
+      _ ->
+        {:error,
+         field: :base,
+         message:
+           "Registration is disabled. Please use the join form or contact an administrator."}
+    end
+  end
+end