Small code cleaning in the iface package. These changes necessary to
get a clean code in case if we involve more platforms. The OS related
functions has been distributed into separate files and it has been
mixed with not OS related logic. The goal is to get a clear picture
of the layer between WireGuard and business logic.
* 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.
Adding --external-ip-map and --dns-resolver-address to up command and shorthand option to global flags.
Refactor get and read config functions with new ConfigInput type.
updated cobra package to latest release.
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
Added DNS update protocol message
Added sync to clients
Update nameserver API with new fields
Added default NS groups
Added new dns-name flag for the management service append to peer DNS label
