@GetMapping("getImageCaptcha")
@ApiImplicitParam(name = "scope", allowableValues = ImgCaptchaType.allowableValues)
fun getImageCaptcha(scope: String, response: HttpServletResponse): ResponseEntity<*> {
    if (!ImgCaptchaType.allowableValueList.contains(scope)) {
        return Result.badRequest(mapOf("scope" to "invalid scope"))
    }
    val captcha = RandomStringUtils.randomAlphanumeric(6)
    CaptchaUtil.outPng(request, response)
    session.setAttribute(scope, captcha)
    return Result.ok()
}

@PutMapping("sendPhoneCaptcha")
@ApiImplicitParam(name = "scope", allowableValues = PhoneCaptchaType.allowableValues)
fun sendPhoneCaptcha(phoneNumber: String, scope: String): ResponseEntity<*> {
        if (!PhoneCaptchaType.allowableValueList.contains(scope)) {
            return Result.badRequest(mapOf("scope" to "invalid scope"))
        }
        // ...
}

object PhoneCaptchaType {
    const val MERCHANT_LOGIN = "PHONE_CAPTCHA_MERCHANT_LOGIN"
    const val ADMIN_FORGET_PASS = "PHONE_CAPTCHA_ADMIN_FORGET_PASS"

    const val allowableValues = "$MERCHANT_LOGIN,$ADMIN_FORGET_PASS"

    val allowableValueList by lazy {
        allowableValues.split(",")
    }
}

object ImgCaptchaType {
    const val ADMIN_LOGIN = "IMG_CAPTCHA_MERCHANT_LOGIN"

    const val allowableValues = ADMIN_LOGIN

    val allowableValueList by lazy {
        allowableValues.split(",")
    }
}