@type t() :: %OpenFeature.EvaluationDetails{
  error_code: OpenFeature.Types.error_code() | nil,
  error_message: binary() | nil,
  flag_metadata: OpenFeature.Types.flag_metadata() | nil,
  key: binary(),
  reason: OpenFeature.Types.reason() | nil,
  value: OpenFeature.Types.flag_value(),
  variant: binary() | nil
}