+ @doc """
+ Gets or creates Pleroma.Registration record from Ueberauth assigns.
+ Note: some strategies (like `keycloak`) might need extra configuration to fill `uid` from callback response —
+ see [`docs/config.md`](docs/config.md).
+ """
+ def get_registration(%Plug.Conn{assigns: %{ueberauth_auth: %{uid: nil}}}),
+ do: {:error, :missing_uid}
+