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- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch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/providers/perfectprivacy/servers.go

@@ -0,0 +1,73 @@
+package perfectprivacy
+
+import (
+	"context"
+	"fmt"
+	"net/url"
+	"sort"
+	"strings"
+
+	"github.com/qdm12/gluetun-servers/pkg/models"
+	"github.com/qdm12/gluetun-servers/pkg/updaters/common"
+	"github.com/qdm12/gluetun-servers/pkg/updaters/openvpn"
+)
+
+func (u *Updater) FetchServers(ctx context.Context, minServers int) (
+	servers []models.Server, err error,
+) {
+	zipURL := url.URL{
+		Scheme: "https",
+		Host:   "www.perfect-privacy.com",
+		Path:   "/downloads/openvpn/get",
+	}
+	values := make(url.Values)
+	values.Set("system", "linux")
+	values.Set("scope", "server")
+	values.Set("filetype", "zip")
+	values.Set("protocol", "udp") // all support both TCP and UDP
+	zipURL.RawQuery = values.Encode()
+
+	contents, err := u.unzipper.FetchAndExtract(ctx, zipURL.String())
+	if err != nil {
+		return nil, err
+	}
+
+	cts := make(cityToServer)
+
+	for fileName, content := range contents {
+		err := addServerFromOvpn(cts, fileName, content)
+		if err != nil {
+			u.warner.Warn(err.Error() + " in " + fileName)
+		}
+	}
+
+	if len(cts) < minServers {
+		return nil, fmt.Errorf("%w: %d and expected at least %d",
+			common.ErrNotEnoughServers, len(cts), minServers)
+	}
+
+	servers = cts.toServersSlice()
+
+	sort.Sort(models.SortableServers(servers))
+
+	return servers, nil
+}
+
+func addServerFromOvpn(cts cityToServer,
+	fileName string, content []byte,
+) (err error) {
+	if !strings.HasSuffix(fileName, ".conf") {
+		return nil // not an OpenVPN file
+	}
+
+	ips, err := openvpn.ExtractIPs(content)
+	if err != nil {
+		return err
+	}
+
+	city := parseFilename(fileName)
+
+	cts.add(city, ips)
+
+	return nil
+}