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- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch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

@@ -0,0 +1,90 @@
+package ipvanish
+
+import (
+	"context"
+	"fmt"
+	"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"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+func (u *Updater) FetchServers(ctx context.Context, minServers int) (
+	servers []models.Server, err error,
+) {
+	const url = "https://configs.ipvanish.com/openvpn/v2.6.0-0/configs.zip"
+	contents, err := u.unzipper.FetchAndExtract(ctx, url)
+	if err != nil {
+		return nil, err
+	} else if len(contents) < minServers {
+		return nil, fmt.Errorf("%w: %d and expected at least %d",
+			common.ErrNotEnoughServers, len(contents), minServers)
+	}
+
+	hts := make(hostToServer)
+
+	titleCaser := cases.Title(language.English)
+	for fileName, content := range contents {
+		if !strings.HasSuffix(fileName, ".ovpn") {
+			continue // not an OpenVPN file
+		}
+
+		tcp, udp, err := openvpn.ExtractProto(content)
+		if err != nil {
+			// treat error as warning and go to next file
+			u.warner.Warn(err.Error() + " in " + fileName)
+			continue
+		}
+
+		hostname, warning, err := openvpn.ExtractHost(content)
+		if warning != "" {
+			u.warner.Warn(warning)
+		}
+		if err != nil {
+			// treat error as warning and go to next file
+			u.warner.Warn(err.Error() + " in " + fileName)
+			continue
+		}
+
+		country, city, err := parseFilename(fileName, hostname, titleCaser)
+		if err != nil {
+			// treat error as warning and go to next file
+			u.warner.Warn(err.Error() + " in " + fileName)
+			continue
+		}
+
+		hts.add(hostname, country, city, tcp, udp)
+	}
+
+	if len(hts) < minServers {
+		return nil, fmt.Errorf("%w: %d and expected at least %d",
+			common.ErrNotEnoughServers, len(hts), minServers)
+	}
+
+	hosts := hts.toHostsSlice()
+	resolveSettings := parallelResolverSettings(hosts)
+	hostToIPs, warnings, err := u.parallelResolver.Resolve(ctx, resolveSettings)
+	for _, warning := range warnings {
+		u.warner.Warn(warning)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	if len(hostToIPs) < minServers {
+		return nil, fmt.Errorf("%w: %d and expected at least %d",
+			common.ErrNotEnoughServers, len(servers), minServers)
+	}
+
+	hts.adaptWithIPs(hostToIPs)
+
+	servers = hts.toServersSlice()
+
+	sort.Sort(models.SortableServers(servers))
+
+	return servers, nil
+}