Maint: refactor VPN configuration structure

- Paves the way for Wireguard
- VPN struct contains Type, Openvpn and Provider configurations
- OpenVPN specific options (e.g. client key) moved from Provider to Openvpn configuration struct
- Move Provider configuration from OpenVPN configuration to VPN
- HTTP control server returns only openvpn settings (not provider settings)

internal/provider/cyberghost/openvpnconf.go

@@ -71,7 +71,7 @@ func (c *Cyberghost) BuildConf(connection models.OpenVPNConnection,
 		lines = append(lines, "mssfix "+strconv.Itoa(int(settings.MSSFix)))
 	}
 
-	if settings.Provider.ExtraConfigOptions.OpenVPNIPv6 {
+	if settings.IPv6 {
 		lines = append(lines, "tun-ipv6")
 	} else {
 		lines = append(lines, `pull-filter ignore "route-ipv6"`)
@@ -81,9 +81,9 @@ func (c *Cyberghost) BuildConf(connection models.OpenVPNConnection,
 	lines = append(lines, utils.WrapOpenvpnCA(
 		constants.CyberghostCertificate)...)
 	lines = append(lines, utils.WrapOpenvpnCert(
-		settings.Provider.ExtraConfigOptions.ClientCertificate)...)
+		settings.ClientCrt)...)
 	lines = append(lines, utils.WrapOpenvpnKey(
-		settings.Provider.ExtraConfigOptions.ClientKey)...)
+		settings.ClientKey)...)
 
 	lines = append(lines, "")