IPv6 resolution is incorrect in TURN

[ehfd]

TURN pointing to an IPv6 server requires brackets around IPv6 IPs.

• [ ] The current implementation does not place brackets around such IPs, which lead to issues in IPv6-only networks. This must be fixed to represent all cases (IPv4-only, mixed IPv4-IPv6, IPv6-only).

  export SELKIES_TURN_HOST="${SELKIES_TURN_HOST:-$(dig TXT +short @ns1.google.com o-o.myaddr.l.google.com 2>/dev/null | { read output; if [ -z "$output" ] || echo "$output" | grep -q '^;;'; then exit 1; else echo "$(echo $output | sed 's,\",,g')"; fi } || dig -6 TXT +short @ns1.google.com o-o.myaddr.l.google.com 2>/dev/null | { read output; if [ -z "$output" ] || echo "$output" | grep -q '^;;'; then exit 1; else echo "$(echo $output | sed 's,\",,g')"; fi } || hostname -I 2>/dev/null | awk '{print $1; exit}' || echo '127.0.0.1')}"
  export TURN_EXTERNAL_IP="${TURN_EXTERNAL_IP:-$(getent ahosts ${SELKIES_TURN_HOST} | awk '{print $1; exit}')}"

• [ ] Note that the effect of brackets in IPv6 IPs combined with https://gstreamer.freedesktop.org/documentation/webrtc/index.html#webrtcbin:turn-server must also be considered.
• [ ] And of course, https://github.com/selkies-project/docker-nvidia-egl-desktop and https://github.com/selkies-project/docker-nvidia-glx-desktop must also be updated in accordance.
• [ ] Documentation/command-line help message must also specify that SELKIES_TURN_HOST requires [] in IPv6.

[ehfd]

@robballantyne This may be the cause of certain issues in several platforms using @ai-dock including Vast.AI.