message: fix: Add card to PaymentMethodDetails
diff: use crate::params::Timestamp;
  +use crate::resources::card::{Card, CardBrand, CardType};
  use serde_derive::{Deserialize, Serialize};
  /// An enum representing the possible values of a `BankAccount`'s `account_holder_type` field.
  @@ -119,10 +120,45 @@ pub struct PackageDimensions {
  pub width: f64,
  }
  +#[derive(Clone, Debug, Default, Deserialize, Serialize)]
  +pub struct PaymentMethodCard {
  + /// Can be `American Express`, `Diners Club`, `Discover`, `JCB`, `MasterCard`, `UnionPay`, `Visa`, or `Unknown`.
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub brand: Option<CardBrand>,
  +
  + /// Two-letter ISO code representing the country of the card.
  + ///
  + /// You could use this attribute to get a sense of the international breakdown of cards you've collected.
  + pub country: String,
  +
  + /// Two-digit number representing the card's expiration month.
  + pub exp_month: i64,
  +
  + /// Four-digit number representing the card's expiration year.
  + pub exp_year: i64,
  +
  + /// Uniquely identifies this particular card number.
  + ///
  + /// You can use this attribute to check whether two customers who've signed up with you are using the same card number, for example.
  + pub fingerprint: String,
  +
  + /// Card funding type.
  + ///
  + /// Can be `credit`, `debit`, `prepaid`, or `unknown`.
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub funding: Option<CardType>,
  +
  + /// The last four digits of the card.
  + pub last4: String,
  +}
  +
  // TODO: Implement
  /// This type is a stub that still needs to be implemented.
  #[derive(Clone, Debug, Deserialize, Serialize)]
  -pub struct PaymentMethodDetails {}
  +pub struct PaymentMethodDetails {
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub card: Option<PaymentMethodCard>,
  +}
  /// Period is a structure representing a start and end dates.
  #[derive(Clone, Debug, Deserialize, Serialize)]
  