To protect the endpoint used to send phone number verification code from
potential abuse, we add waiting time between subsequent requests.

1. 1st SMS send request - no waiting time
2. 2nd SMS send request - wait 1 minute
3. 3rd SMS send request - wait 3 minutes
4. 4th SMS send request - wait 5 minutes
5. 5th (and so on) SMS send request - wait 10 minutes

Changelog: changed
EE: true