CheckoutPaymentMethod .FromJson method doesn't preserve GooglePayToken integrity

[PG-RichT]

Describe the bug

CheckoutPaymentMethod .FromJson method doesn't preserve GooglePayToken integrity causing failure to complete payment.

On submission of PaymentRequest, the following error is returned from the Adyen API:

{
  "status": 422,
  "errorCode": "5_202",
  "message": "Invalid PayWithGoogle Token",
  "errorType": "validation",
  "pspReference": "VMN8WMH3WFRLLR65"
}

In the Adyen documentation for handling errors with Google Pay (https://docs.adyen.com/development-resources/error-codes/#5202-invalid-paywithgoogle-token), you state:

Make sure that you are sending in the correct token. Do not escape the stringified JSON; send it as it is.

To Reproduce
Steps to reproduce the behavior:

Using the C# Adyen client library, receive a MakePayment payload from Adyen Dropin client and create a CheckoutPaymentMethod object using the static FromJson method and the received paymentMethod object contents.

On receipt the paymentMethod contents looks like something this. Note the encoding at the end of each property value inside the signedMessage object:

{
  "type": "paywithgoogle",
  "googlePayToken": "{\"signature\":\"MEYCIQDBZEzdH0afYNxdkFD8L9KduGfFO6ZwLma9KxkDzUOqBwIhAJRUpkA7Dhvxub2RZc5fk67xKmjz4JxYYmp0w20j06nB\",\"protocolVersion\":\"ECv1\",\"signedMessage\":\"{\\\"encryptedMessage\\\":\\\"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\\\\u003d\\\\u003d\\\",\\\"ephemeralPublicKey\\\":\\\"BMzHuZyjSIngfmV6FVt5PRu5km/ESAqPfe4xXjmUIYyol9THh16Y1r4ZzHyfo3NFtcksteOOKlpW7qMln791KUE\\\\u003d\\\",\\\"tag\\\":\\\"O2FfG8JBYMGLI/6U0dm0Qm57APD7ivme8xxPZBSfKBM\\\\u003d\\\"}\"}",
  "googlePayCardNetwork": "MASTERCARD",
  "checkoutAttemptId": "bd2828fb-2243-467d-9f64-68cab32ea99717206059619985659D9DFED0E623007C65F15855C2CA4F4874C10AEB4F7A0462D72DC2C82C648"
}

After creating an object using the FromJson method, note the change to the end of the property values inside the nested signedMessage object that causes the issue:

{
  "signature": "MEYCIQDBZEzdH0afYNxdkFD8L9KduGfFO6ZwLma9KxkDzUOqBwIhAJRUpkA7Dhvxub2RZc5fk67xKmjz4JxYYmp0w20j06nB",
  "protocolVersion": "ECv1",
  "signedMessage": "{\"encryptedMessage\":\"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\\u003d\\u003d\",\"ephemeralPublicKey\":\"BMzHuZyjSIngfmV6FVt5PRu5km/ESAqPfe4xXjmUIYyol9THh16Y1r4ZzHyfo3NFtcksteOOKlpW7qMln791KUE\\u003d\",\"tag\":\"O2FfG8JBYMGLI/6U0dm0Qm57APD7ivme8xxPZBSfKBM\\u003d\"}"
}

Expected behavior
The contents of the googlePayToken should be preserved and not altered in any way.

Desktop (please complete the following information):

• Dropin, v5.66.1
• dotNet library v17.0.0
• OS: Windows
• Browser: Chrome
• Version: 126.0.6478.127 (Official Build) (64-bit)

[PG-RichT]

For anyone else that finds themselves here, I resolved the issue. It helps if your incoming payload is mapped to the 'Adyen.Model.Checkout.PaymentRequest' model, then all is well.