I want to generate a token and insert it to my mysql db, this is the current code, im just passing '123'. mix phoenix.gen.secret can generate random string how can i use it to my controller?

```
def create(conn, %{"token" => token_params}) do
token_params = Map.merge(token_params, %{"value" => "123"})

changeset = Token.changeset(%Token{}, token_params)

case Repo.insert(changeset) do
  {:ok, token} ->
    conn
    |> put_status(:created)
    |> put_resp_header("location", token_path(conn, :show, token))
    |> render("show.json", token: token)
  {:error, changeset} ->
    conn
    |> put_status(:unprocessable_entity)
    |> render(MyApp.ChangesetView, "error.json", changeset: changeset)
  end

```

end