Example

$ curl https://example.com/update -u hostname:password
> success

$ curl https://hostname:password@example.com/update?ip=192.0.2.8
> success

$ dig +short hostname.example.com
> 198.51.100.5
    
More examples
$ curl https://.../update?hostname=hostname&password=password
> success

$ curl https://.../update?ip=2001:DB8::1968:08:17
> success

$ dig +short hostname.example.com aaaa
> 2001:db8::1968:8:17

$ curl https://.../update?ip=2001:DB8::1968:08:17&ip=192.0.2.8&ip=198.51.100.5
> success

$ dig +short hostname.example.com aaaa
> 2001:db8::1968:8:17
$ dig +short hostname.example.com a
> 192.0.2.8
  198.51.100.5
      

Tips