POST /v2/refunds/
/v2/refunds/
GET /v2/refunds/{id}
/v2/refunds/{id}
GET /v2/refunds/
@spec create(map()) :: {:ok, map()} | {:error, term()}
amount
payment
@spec get(String.t()) :: {:ok, map()} | {:error, term()}
@spec list() :: {:ok, map()} | {:error, term()}