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- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch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

@@ -0,0 +1,45 @@
+package hidemyass
+
+import (
+	"context"
+	"net/http"
+	"strings"
+
+	"github.com/qdm12/gluetun-servers/pkg/updaters/openvpn"
+)
+
+func getAllHostToURL(ctx context.Context, client *http.Client) (
+	tcpHostToURL, udpHostToURL map[string]string, err error,
+) {
+	tcpHostToURL, err = getHostToURL(ctx, client, "TCP")
+	if err != nil {
+		return nil, nil, err
+	}
+
+	udpHostToURL, err = getHostToURL(ctx, client, "UDP")
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return tcpHostToURL, udpHostToURL, nil
+}
+
+func getHostToURL(ctx context.Context, client *http.Client, protocol string) (
+	hostToURL map[string]string, err error,
+) {
+	const baseURL = "https://vpn.hidemyass.com/vpn-config"
+	indexURL := baseURL + "/" + strings.ToUpper(protocol) + "/"
+
+	urls, err := fetchIndex(ctx, client, indexURL)
+	if err != nil {
+		return nil, err
+	}
+
+	const failEarly = true
+	hostToURL, errors := openvpn.FetchMultiFiles(ctx, client, urls, failEarly)
+	if len(errors) > 0 {
+		return nil, errors[0]
+	}
+
+	return hostToURL, nil
+}