Versioning of UI and grpc-agent for passing version (#324)

Send Desktop UI client version as user-agent to daemon

This is sent on every login request to the management

Parse the GRPC context on the system package and 
retrieves the user-agent

Management receives the new UIVersion field and 
store in the Peer's system meta

client/system/info.go

@@ -1,5 +1,11 @@
 package system
 
+import (
+	"context"
+	"google.golang.org/grpc/metadata"
+	"strings"
+)
+
 // this is the wiretrustee version
 // will be replaced with the release version when using goreleaser
 var version = "development"
@@ -16,8 +22,31 @@ type Info struct {
 	Hostname           string
 	CPUs               int
 	WiretrusteeVersion string
+	UIVersion          string
 }
 
-func WiretrusteeVersion() string {
+// NetbirdVersion returns the Netbird version
+func NetbirdVersion() string {
 	return version
 }
+
+// extractUserAgent extracts Netbird's agent (client) name and version from the outgoing context
+func extractUserAgent(ctx context.Context) string {
+	md, hasMeta := metadata.FromOutgoingContext(ctx)
+	if hasMeta {
+		agent, ok := md["user-agent"]
+		if ok {
+			nbAgent := strings.Split(agent[0], " ")[0]
+			if strings.HasPrefix(nbAgent, "netbird") {
+				return nbAgent
+			}
+			return ""
+		}
+	}
+	return ""
+}
+
+// GetDesktopUIUserAgent returns the Desktop ui user agent
+func GetDesktopUIUserAgent() string {
+	return "netbird-desktop-ui/" + NetbirdVersion()
+}