refactoring around the new sdk approach (#34)

sdk/model.go

@@ -0,0 +1,23 @@
+package sdk
+
+type BackendMode string
+
+const (
+	ProxyBackendMode     BackendMode = "proxy"
+	WebBackendMode       BackendMode = "web"
+	TcpTunnelBackendMode BackendMode = "tcpTunnel"
+	UdpTunnelBackendMode BackendMode = "udpTunnel"
+)
+
+type ShareMode string
+
+const (
+	PrivateShareMode ShareMode = "private"
+	PublicShareMode  ShareMode = "public"
+)
+
+type ShareRequest struct {
+	BackendMode BackendMode
+	ShareMode   ShareMode
+	Target      string
+}