feat: add join confirmation and mail templating

lib/membership/membership.ex

@@ -30,6 +30,7 @@ defmodule Mv.Membership do
   import Ash.Expr
   alias Ash.Error.Query.NotFound, as: NotFoundError
   alias Mv.Membership.JoinRequest
+  alias MvWeb.Emails.JoinConfirmationEmail
 
   admin do
     show? true
@@ -85,7 +86,7 @@ defmodule Mv.Membership do
     end
 
     resource Mv.Membership.JoinRequest do
-      define :submit_join_request, action: :submit
+      # submit_join_request/2 implemented as custom function below (create + send email)
     end
   end
 
@@ -350,6 +351,47 @@ defmodule Mv.Membership do
     |> then(&Ash.read_one(query, &1))
   end
 
+  @doc """
+  Creates a join request (submit flow) and sends the confirmation email.
+
+  Generates a confirmation token if not provided in attrs (e.g. for tests, pass
+  `:confirmation_token` to get a known token). On success, sends one email with
+  the confirm link to the request email.
+
+  ## Options
+    - `:actor` - Must be nil for public submit (policy allows only unauthenticated).
+
+  ## Returns
+    - `{:ok, request}` - Created JoinRequest in status pending_confirmation
+    - `{:error, error}` - Validation or authorization error
+  """
+  def submit_join_request(attrs, opts \\ []) do
+    actor = Keyword.get(opts, :actor)
+    token = Map.get(attrs, :confirmation_token) || generate_confirmation_token()
+
+    attrs_with_token =
+      attrs |> Map.drop([:confirmation_token]) |> Map.put(:confirmation_token, token)
+
+    case Ash.create(JoinRequest, attrs_with_token,
+           action: :submit,
+           actor: actor,
+           domain: __MODULE__
+         ) do
+      {:ok, request} ->
+        JoinConfirmationEmail.send(request.email, token)
+        {:ok, request}
+
+      error ->
+        error
+    end
+  end
+
+  defp generate_confirmation_token do
+    32
+    |> :crypto.strong_rand_bytes()
+    |> Base.url_encode64(padding: false)
+  end
+
   @doc """
   Confirms a join request by token (public confirmation link).