Get pending downgrade

curl --request GET \
  --url https://www.myshop.com/apps/memberships/cp/api/subscription-contract-details/{contractId}/pending-downgrade

{
  "shop": "<string>",
  "contractId": 123,
  "waitTillTimestamp": "<string>",
  "oldLineId": "<string>",
  "oldVariantId": "<string>",
  "newVariantId": "<string>",
  "sellingPlanId": "<string>",
  "sellingPlanName": "<string>",
  "oldPrice": 123,
  "newPrice": 123,
  "newCustomerTag": "<string>",
  "oldCustomerTags": "<string>",
  "newOrderTag": "<string>",
  "eventSource": "<string>",
  "retryCount": 123,
  "customerId": 123,
  "executionArn": "<string>"
}