Obtain PIA v4 server information from API (#257)

- Obtain CN for port forwarding https verification
- Obtain for each server if they support port forwarding
- Obtain for each server their IP address for openvpn UDP and openvpn TCP (one for each)
- Updater program updated to use API
- Hardcoded values updated for PIA v3 and v4 servers
- Clearer separation between pia v3 and v4
- Fixes #250

internal/models/server.go

@@ -8,11 +8,32 @@ import (
 )
 
 type PIAServer struct {
+	Region      string           `json:"region"`
+	PortForward bool             `json:"port_forward"`
+	OpenvpnUDP  PIAServerOpenvpn `json:"openvpn_udp"`
+	OpenvpnTCP  PIAServerOpenvpn `json:"openvpn_tcp"`
+}
+
+type PIAServerOpenvpn struct {
+	IPs []net.IP `json:"ips"`
+	CN  string   `json:"cn"`
+}
+
+func (p *PIAServerOpenvpn) String() string {
+	return fmt.Sprintf("models.PIAServerOpenvpn{CN: %q, IPs: %s}", p.CN, goStringifyIPs(p.IPs))
+}
+
+func (p *PIAServer) String() string {
+	return fmt.Sprintf("{Region: %q, PortForward: %t, OpenvpnUDP: %s, OpenvpnTCP: %s}",
+		p.Region, p.PortForward, p.OpenvpnUDP.String(), p.OpenvpnTCP.String())
+}
+
+type PIAOldServer struct {
 	IPs    []net.IP `json:"ips"`
 	Region string   `json:"region"`
 }
 
-func (p *PIAServer) String() string {
+func (p *PIAOldServer) String() string {
 	return fmt.Sprintf("{Region: %q, IPs: %s}", p.Region, goStringifyIPs(p.IPs))
 }