@type t() :: %Oidcc.ClientRegistration.Response{
  client_id: String.t(),
  client_id_issued_at: pos_integer() | :undefined,
  client_secret: String.t() | :undefined,
  client_secret_expires_at: pos_integer() | :undefined,
  extra_fields: %{required(String.t()) => term()},
  registration_access_token: String.t() | :undefined,
  registration_client_uri: :uri_string.uri_string() | :undefined
}