Get Challenge

curl --request GET \
  --url https://api.authsignal.com/v1/challenges

{
  "challengeId": "<string>",
  "verificationMethod": "SMS",
  "phoneNumber": "<string>",
  "email": "<string>",
  "smsChannel": "<string>",
  "expiresAt": 123,
  "action": 123
}