Pull request 1897: nextapi-write-conf

Squashed commit of the following:

commit 72f25ffe73d6b8216b01e590fba66fb5f6944113
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed Jun 28 21:29:04 2023 +0300

    next: add conf writing, validation

internal/dnsforward/config.go

@@ -540,6 +540,7 @@ func (s *Server) prepareIpsetListSettings() (err error) {
 		return s.ipset.init(s.conf.IpsetList)
 	}
 
+	// #nosec G304 -- Trust the path explicitly given by the user.
 	data, err := os.ReadFile(fn)
 	if err != nil {
 		return err