Start SMS Enrollment

curl --request POST \
  --url https://api.authsignal.com/v1/client/user-authenticators/sms \
  --header 'Content-Type: application/json' \
  --data '{
  "phoneNumber": "<string>",
  "smsChannel": "DEFAULT"
}'

{
  "userAuthenticatorId": "<string>",
  "userId": "<string>"
}