t() :: %Money.ExchangeRates.Config{
  api_module: module() | nil,
  cache_module: module() | nil,
  callback_module: module() | nil,
  log_levels: map(),
  preload_historic_rates:
    Date.t() | Date.Range.t() | {Date.t(), Date.t()} | nil,
  retrieve_every: non_neg_integer() | nil,
  retriever_options: map() | nil,
  verify_peer: boolean()
}