refactor(storage): new storage file structure

- new directory structure containing manifest.json and one json file per provider, by default.
- the manifest.json file can specify a filepath for each vpn provider
- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch
- `STORAGE_SERVERS_DIRECTORY_PATH` replaces `STORAGE_FILEPATH` (which is now a migration source only). It sets the directory where server manifest and per-provider JSON files are stored (default: `/gluetun/servers/`).
- First-run migration: On startup, gluetun checks for the old /gluetun/servers.json file; if found and no new manifest exists, it automatically migrates all data to /gluetun/servers/ directory structure
- Silent fallback: If legacy file isn't found, uses the new directory path normally
- Legacy cleanup: After successful migration, attempts to remove the old fat JSON file (logs warning only if removal fails, e.g., read-only bind mounts)

gluetun-servers/pkg/updaters/openvpn/extract.go

@@ -0,0 +1,93 @@
+package openvpn
+
+import (
+	"errors"
+	"fmt"
+	"net/netip"
+	"sort"
+	"strings"
+)
+
+func ExtractProto(b []byte) (tcp, udp bool, err error) {
+	lines := strings.Split(string(b), "\n")
+	const protoPrefix = "proto "
+	for _, line := range lines {
+		if !strings.HasPrefix(line, protoPrefix) {
+			continue
+		}
+		s := strings.TrimPrefix(line, protoPrefix)
+		s = strings.TrimSpace(s)
+		s = strings.ToLower(s)
+		switch s {
+		case "tcp", "tcp4", "tcp6", "tcp-client":
+			return true, false, nil
+		case "udp", "udp4", "udp6":
+			return false, true, nil
+		default:
+			return false, false, fmt.Errorf("unknown protocol: %s", s)
+		}
+	}
+
+	// default is UDP if unspecified in openvpn configuration
+	return false, true, nil
+}
+
+func ExtractHost(b []byte) (host, warning string, err error) {
+	const (
+		rejectIP     = true
+		rejectDomain = false
+	)
+	hosts := extractRemoteHosts(b, rejectIP, rejectDomain)
+	if len(hosts) == 0 {
+		return "", "", errors.New("remote host not found")
+	} else if len(hosts) > 1 {
+		warning = fmt.Sprintf(
+			"only using the first host %q and discarding %d other hosts",
+			hosts[0], len(hosts)-1)
+	}
+	return hosts[0], warning, nil
+}
+
+func ExtractIPs(b []byte) (ips []netip.Addr, err error) {
+	const rejectIP, rejectDomain = false, true
+	ipStrings := extractRemoteHosts(b, rejectIP, rejectDomain)
+	if len(ipStrings) == 0 {
+		return nil, errors.New("remote IP not found")
+	}
+
+	sort.Slice(ipStrings, func(i, j int) bool {
+		return ipStrings[i] < ipStrings[j]
+	})
+
+	ips = make([]netip.Addr, len(ipStrings))
+	for i := range ipStrings {
+		ips[i], err = netip.ParseAddr(ipStrings[i])
+		if err != nil {
+			return nil, fmt.Errorf("parsing IP address: %w", err)
+		}
+	}
+
+	return ips, nil
+}
+
+func extractRemoteHosts(content []byte, rejectIP, rejectDomain bool) (hosts []string) {
+	lines := strings.Split(string(content), "\n")
+	for _, line := range lines {
+		line = strings.TrimSpace(line)
+		if !strings.HasPrefix(line, "remote ") {
+			continue
+		}
+		fields := strings.Fields(line)
+		if len(fields) == 1 || fields[1] == "" {
+			continue
+		}
+		host := fields[1]
+		_, err := netip.ParseAddr(host)
+		if (rejectIP && err == nil) ||
+			(rejectDomain && err != nil) {
+			continue
+		}
+		hosts = append(hosts, host)
+	}
+	return hosts
+}