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- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch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

@@ -0,0 +1,75 @@
+package surfshark
+
+import (
+	"context"
+	"strings"
+
+	"github.com/qdm12/gluetun-servers/pkg/updaters/common"
+	"github.com/qdm12/gluetun-servers/pkg/updaters/openvpn"
+	"github.com/qdm12/gluetun-servers/pkg/updaters/providers/surfshark/servers"
+)
+
+func addOpenVPNServersFromZip(ctx context.Context,
+	unzipper common.Unzipper, hts hostToServers) (
+	warnings []string, err error,
+) {
+	const url = "https://my.surfshark.com/vpn/api/v1/server/configurations"
+	contents, err := unzipper.FetchAndExtract(ctx, url)
+	if err != nil {
+		return nil, err
+	}
+
+	hostnamesDone := hts.toHostsSlice()
+	hostnamesDoneSet := make(map[string]struct{}, len(hostnamesDone))
+	for _, hostname := range hostnamesDone {
+		hostnamesDoneSet[hostname] = struct{}{}
+	}
+
+	locationData := servers.LocationData()
+	hostToLocation := hostToLocation(locationData)
+
+	for fileName, content := range contents {
+		if !strings.HasSuffix(fileName, ".ovpn") {
+			continue // not an OpenVPN file
+		}
+
+		host, warning, err := openvpn.ExtractHost(content)
+		if warning != "" {
+			warnings = append(warnings, warning)
+		}
+		if err != nil {
+			// treat error as warning and go to next file
+			warning := err.Error() + " in " + fileName
+			// TODO gather location data for IP address Openvpn files
+			// and process those when this error triggers.
+			warnings = append(warnings, warning)
+			continue
+		}
+
+		_, ok := hostnamesDoneSet[host]
+		if ok {
+			continue // already done in API
+		}
+
+		tcp, udp, err := openvpn.ExtractProto(content)
+		if err != nil {
+			// treat error as warning and go to next file
+			warning := err.Error() + " in " + fileName
+			warnings = append(warnings, warning)
+			continue
+		}
+
+		data, err := getHostInformation(host, hostToLocation)
+		if err != nil {
+			// treat error as warning and go to next file
+			warning := err.Error()
+			warnings = append(warnings, warning)
+			continue
+		}
+
+		hts.addOpenVPN(host, data.Region, data.Country, data.City,
+			data.RetroLoc, tcp, udp)
+	}
+
+	return warnings, nil
+}