Feature: Multiple IPs for each Torguard server

- Fallback on IP from configuration file if DNS resolution fails
- Download both TCP and UDP zip files to detect support for each
- Filter servers by supported network protocol
-

internal/updater/providers/torguard/hosttoserver.go

@@ -0,0 +1,55 @@
+package torguard
+
+import (
+	"net"
+
+	"github.com/qdm12/gluetun/internal/models"
+)
+
+type hostToServer map[string]models.TorguardServer
+
+func (hts hostToServer) add(host, country, city string, tcp, udp bool, ip net.IP) {
+	server, ok := hts[host]
+	if !ok {
+		server.Hostname = host
+		server.Country = country
+		server.City = city
+		server.IPs = append(server.IPs, ip) // used if DNS resolution fails downstream
+	}
+	if tcp {
+		server.TCP = tcp
+	}
+	if udp {
+		server.UDP = udp
+	}
+	hts[host] = server
+}
+
+func (hts hostToServer) toHostsSlice() (hosts []string) {
+	hosts = make([]string, 0, len(hts))
+	for host := range hts {
+		hosts = append(hosts, host)
+	}
+	return hosts
+}
+
+func (hts hostToServer) adaptWithIPs(hostToIPs map[string][]net.IP) {
+	for host, IPs := range hostToIPs {
+		server := hts[host]
+		server.IPs = IPs
+		hts[host] = server
+	}
+	for host, server := range hts {
+		if len(server.IPs) == 0 {
+			delete(hts, host)
+		}
+	}
+}
+
+func (hts hostToServer) toServersSlice() (servers []models.TorguardServer) {
+	servers = make([]models.TorguardServer, 0, len(hts))
+	for _, server := range hts {
+		servers = append(servers, server)
+	}
+	return servers
+}