Issue Service Credit response body change

As of November 23, 2021, the Issue Service Credit API endpoint will respond with a new body:

 {
  "id": "Integer",
  "amount_in_cents": "Integer",
  "ending_balance_in_cents": "Integer",
  "entry_type": "String",
  "memo": "String"
}

Previously, this endpoint was returning just a status code with no body.