Handle original search domains in resolv.conf type implementations.
- parse the original resolv.conf file
- merge the search domains
- ignore the domain keyword
- append any other config lines (sortstlist, options)
- fix read origin resolv.conf from bkp in resolvconf implementation
- fix line length validation
- fix number of search domains validation
* Disable upstream DNS resolver after several tries and fails
* Add tests for upstream fails
* Use an extra flag to disable domains in DNS upstreams
* Fix hashing IPs of nameservers for updates.
Added host configurators for Linux, Windows, and macOS.
The host configurator will update the peer system configuration
directing DNS queries according to its capabilities.
Some Linux distributions don't support split (match) DNS or custom ports,
and that will be reported to our management system in another PR
