Reliability: backport tight crypto API from on_the_map

[cognivore]

Why?

In DoAuth.Crypto, we allow for loosey-goosey calls to sign. For example, we allow raw iolists. It contradicts the uptight coding principles.

How?

• [ ] Only support T.t() | list(T.t()) as it is implemented in on_the_map.

  @doc """
  Wrapper around detached signatures that creates an object tracking
  corresponding public key.
  Note that we allow "Uptight iolist" as a message, which is a list of `Uptight.Text` objects.
  """
  @spec sign(T.t() | list(T.t()), keypair()) :: detached_sig()
  def sign(msg, kp) do
  sign_raw(msg |> unwrap_message(), kp |> unwrap_keypair())
  end
  
  defp unwrap_message(%T{} = msg) do
  msg |> T.un()
  end
  
  defp unwrap_message(msg) when is_list(msg) do
  msg |> map(&T.un/1)
  end
  
  defp unwrap_keypair(%{secret: _, public: _} = kp) do
  kp |> map(&Binary.un/1)
  end
  
  defp sign_raw(msg, %{secret: sk, public: pk}) do
  %{public: pk, signature: C.sign_detached(msg, sk)} |> map(&Binary.new!/1)
  end

• [ ] Make sure that we never expose loose interfaces and all the _raw functions are private, unless we have a good reason to have them public.