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- each vpn provider json data file can contain the `"preferred": true` field to enforce it is used even if outdated, unless there is a version mismatch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

@@ -0,0 +1,102 @@
+package surfshark
+
+import (
+	"net/netip"
+
+	"github.com/qdm12/gluetun-servers/pkg/constants"
+	"github.com/qdm12/gluetun-servers/pkg/models"
+)
+
+type hostToServers map[string][]models.Server
+
+func (hts hostToServers) addOpenVPN(host, region, country, city,
+	retroLoc string, tcp, udp bool,
+) {
+	// Check for existing server for this host and OpenVPN.
+	servers := hts[host]
+	for i, existingServer := range servers {
+		if existingServer.Hostname != host ||
+			existingServer.VPN != constants.OpenVPN {
+			continue
+		}
+
+		// Update OpenVPN supported protocols and return
+		if !existingServer.TCP {
+			servers[i].TCP = tcp
+		}
+		if !existingServer.UDP {
+			servers[i].UDP = udp
+		}
+		return
+	}
+
+	server := models.Server{
+		VPN:      constants.OpenVPN,
+		Region:   region,
+		Country:  country,
+		City:     city,
+		RetroLoc: retroLoc,
+		Hostname: host,
+		TCP:      tcp,
+		UDP:      udp,
+	}
+	hts[host] = append(servers, server)
+}
+
+func (hts hostToServers) addWireguard(host, region, country, city, retroLoc,
+	wgPubKey string,
+) {
+	// Check for existing server for this host and Wireguard.
+	servers := hts[host]
+	for _, existingServer := range servers {
+		if existingServer.Hostname == host &&
+			existingServer.VPN == constants.Wireguard {
+			// No update necessary for Wireguard
+			return
+		}
+	}
+
+	server := models.Server{
+		VPN:      constants.Wireguard,
+		Region:   region,
+		Country:  country,
+		City:     city,
+		RetroLoc: retroLoc,
+		Hostname: host,
+		WgPubKey: wgPubKey,
+	}
+	hts[host] = append(servers, server)
+}
+
+func (hts hostToServers) toHostsSlice() (hosts []string) {
+	const vpnServerTypes = 2 // OpenVPN + Wireguard
+	hosts = make([]string, 0, vpnServerTypes*len(hts))
+	for host := range hts {
+		hosts = append(hosts, host)
+	}
+	return hosts
+}
+
+func (hts hostToServers) adaptWithIPs(hostToIPs map[string][]netip.Addr) {
+	for host, IPs := range hostToIPs {
+		servers := hts[host]
+		for i := range servers {
+			servers[i].IPs = IPs
+		}
+		hts[host] = servers
+	}
+	for host, servers := range hts {
+		if len(servers[0].IPs) == 0 {
+			delete(hts, host)
+		}
+	}
+}
+
+func (hts hostToServers) toServersSlice() (servers []models.Server) {
+	const vpnServerTypes = 2 // OpenVPN + Wireguard
+	servers = make([]models.Server, 0, vpnServerTypes*len(hts))
+	for _, serversForHost := range hts {
+		servers = append(servers, serversForHost...)
+	}
+	return servers
+}