chore(settings): refactor settings processing (#756)

- Better settings tree structure logged using `qdm12/gotree`
- Read settings from environment variables, then files, then secret files
- Settings methods to default them, merge them and override them
- `DNS_PLAINTEXT_ADDRESS` default changed to `127.0.0.1` to use DoT. Warning added if set to something else.
- `HTTPPROXY_LISTENING_ADDRESS` instead of `HTTPPROXY_PORT` (with retro-compatibility)

internal/dns/update.go

@@ -9,17 +9,27 @@ func (l *Loop) updateFiles(ctx context.Context) (err error) {
 	}
 	settings := l.GetSettings()
 
+	unboundSettings, err := settings.DoT.Unbound.ToUnboundFormat()
+	if err != nil {
+		return err
+	}
+
 	l.logger.Info("downloading hostnames and IP block lists")
-	blockedHostnames, blockedIPs, blockedIPPrefixes, errs := l.blockBuilder.All(
-		ctx, settings.BlacklistBuild)
+	blacklistSettings, err := settings.DoT.Blacklist.ToBlacklistFormat()
+	if err != nil {
+		return err
+	}
+
+	blockedHostnames, blockedIPs, blockedIPPrefixes, errs :=
+		l.blockBuilder.All(ctx, blacklistSettings)
 	for _, err := range errs {
 		l.logger.Warn(err.Error())
 	}
 
 	// TODO change to BlockHostnames() when migrating to qdm12/dns v2
-	settings.Unbound.Blacklist.FqdnHostnames = blockedHostnames
-	settings.Unbound.Blacklist.IPs = blockedIPs
-	settings.Unbound.Blacklist.IPPrefixes = blockedIPPrefixes
+	unboundSettings.Blacklist.FqdnHostnames = blockedHostnames
+	unboundSettings.Blacklist.IPs = blockedIPs
+	unboundSettings.Blacklist.IPPrefixes = blockedIPPrefixes
 
-	return l.conf.MakeUnboundConf(settings.Unbound)
+	return l.conf.MakeUnboundConf(unboundSettings)
 }