text: Title: dynDNS: Support multi-IP update in myip= query parameter
  Body: Title says it all. Example log:
  
  ```
  Oct 13 21:49:38 digga desec/www[25547]: update.dedyn.io:443 79.231.19.56 - cmvdo.dedyn.io [13/Oct/2021:19:49:38 +0000] "GET /nic/update?hostname=[...]&myip=2003:[...]:204d,79.[...].56 HTTP/1.0" 400 179 "-" "Deutsche Telekom - Speedport Smart 4 Typ B - 010146.1.1.000.0" TLSv1.3/TLS_AES_256_GCM_SHA384
  ```