dhcpv6-client: T2590: fix vyos-hostsd update for nameserver and search domains (backport #3224)

[c-po]

Change Summary

After migrating from ISC DHCLIENT for IPv6 to wide-dhcp-client the logic which was present to update /etc/resolv.conf with the DHCP specified nameservers and also the search domain list was no longer present.

This commit adds a per interface rendered script to inform vyos-hostsd about the received IPv6 nameservers and search domains.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T2590

Related PR(s)

• dhcpv6-client: T2590: fix vyos-hostsd update for nameserver and search domains #3224

Component(s) name

wide-dhcp-client

Proposed changes

How to test

set interfaces ethernet eth0 address 'dhcpv6'
set system name-server 'eth0'

$ cat /etc/resolv.conf
### Autogenerated by VyOS ###
### Do not edit, your changes will get overwritten ###

# dhcpv6-eth0
nameserver 2001:db8::8888
nameserver 2001:db8::4444

# dhcpv6-eth0
search vyos.net.

Smoketest result

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly