Pull request 2111: 6545-schema-version

Updates #6545.

Squashed commit of the following:

commit b1969128a99ff21c97feb4e7805b4b8133d7122f
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 15 20:04:37 2023 +0300

    home: fix import

commit 872ccea1491a8da76cc24db79247438d0ce4d256
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri Dec 15 20:01:15 2023 +0300

    all: output schema version

internal/configmigrate/v1.go

@@ -0,0 +1,35 @@
+package configmigrate
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/AdguardTeam/golibs/errors"
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// migrateTo1 performs the following changes:
+//
+//	# BEFORE:
+//	# …
+//
+//	# AFTER:
+//	'schema_version': 1
+//	# …
+//
+// It also deletes the unused dnsfilter.txt file, since the following versions
+// store filters in data/filters/.
+func (m *Migrator) migrateTo1(diskConf yobj) (err error) {
+	diskConf["schema_version"] = 1
+
+	dnsFilterPath := filepath.Join(m.workingDir, "dnsfilter.txt")
+	log.Printf("deleting %s as we don't need it anymore", dnsFilterPath)
+	err = os.Remove(dnsFilterPath)
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		log.Info("warning: %s", err)
+
+		// Go on.
+	}
+
+	return nil
+}