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/next/cmd/cmd.go

@@ -19,8 +19,6 @@ import (
 func Main(frontend fs.FS) {
 	start := time.Now()
 
-	// Initial Configuration
-
 	cmdName := os.Args[0]
 	opts, err := parseOptions(cmdName, os.Args[1:])
 	exitCode, needExit := processOptions(opts, cmdName, err)
@@ -39,9 +37,7 @@ func Main(frontend fs.FS) {
 		check(err)
 	}
 
-	// Web Service
-
-	confMgr, err := configmgr.New(opts.confFile, frontend, start)
+	confMgr, err := newConfigMgr(opts.confFile, frontend, start)
 	check(err)
 
 	web := confMgr.Web()
@@ -73,6 +69,15 @@ func ctxWithDefaultTimeout() (ctx context.Context, cancel context.CancelFunc) {
 	return context.WithTimeout(context.Background(), defaultTimeout)
 }
 
+// newConfigMgr returns a new configuration manager using defaultTimeout as the
+// context timeout.
+func newConfigMgr(confFile string, frontend fs.FS, start time.Time) (m *configmgr.Manager, err error) {
+	ctx, cancel := ctxWithDefaultTimeout()
+	defer cancel()
+
+	return configmgr.New(ctx, confFile, frontend, start)
+}
+
 // check is a simple error-checking helper.  It must only be used within Main.
 func check(err error) {
 	if err != nil {