in support-models/src/main/scala/com/gu/support/workers/PaymentFields.scala [57:66]
def parse(value: String): Either[String, StripeSecretKey] =
if (
value.length > 10 &&
(value.startsWith("sk_") || value.startsWith("rk_")) &&
value.forall { char =>
(char >= 'a' && char <= 'z') ||
(char >= 'A' && char <= 'Z') ||
(char >= '0' && char <= '9') ||
char == '_'
}