[management] check and log on new management version (#4029)

This PR enhances the version checker to send a custom User-Agent header when polling for updates, and configures both the management CLI and client UI to use distinct agents. 

- NewUpdate now takes an `httpAgent` string to set the User-Agent header.
- `fetchVersion` builds a custom HTTP request (instead of `http.Get`) and sets the User-Agent.
- Management CLI and client UI now pass `"nb/management"` and `"nb/client-ui"` respectively to NewUpdate.
- Tests updated to supply an `httpAgent` constant.
- Logs if there is a new version available for management

version/update.go

@@ -21,6 +21,7 @@ var (
 // Update fetch the version info periodically and notify the onUpdateListener in case the UI version or the
 // daemon version are deprecated
 type Update struct {
+	httpAgent       string
 	uiVersion       *goversion.Version
 	daemonVersion   *goversion.Version
 	latestAvailable *goversion.Version
@@ -34,7 +35,7 @@ type Update struct {
 }
 
 // NewUpdate instantiate Update and start to fetch the new version information
-func NewUpdate() *Update {
+func NewUpdate(httpAgent string) *Update {
 	currentVersion, err := goversion.NewVersion(version)
 	if err != nil {
 		currentVersion, _ = goversion.NewVersion("0.0.0")
@@ -43,6 +44,7 @@ func NewUpdate() *Update {
 	latestAvailable, _ := goversion.NewVersion("0.0.0")
 
 	u := &Update{
+		httpAgent:       httpAgent,
 		latestAvailable: latestAvailable,
 		uiVersion:       currentVersion,
 		fetchTicker:     time.NewTicker(fetchPeriod),
@@ -112,7 +114,15 @@ func (u *Update) startFetcher() {
 func (u *Update) fetchVersion() bool {
 	log.Debugf("fetching version info from %s", versionURL)
 
-	resp, err := http.Get(versionURL)
+	req, err := http.NewRequest("GET", versionURL, nil)
+	if err != nil {
+		log.Errorf("failed to create request for version info: %s", err)
+		return false
+	}
+
+	req.Header.Set("User-Agent", u.httpAgent)
+
+	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
 		log.Errorf("failed to fetch version info: %s", err)
 		return false