Update hscontrol/types/users.go

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

hscontrol/types/users.go

@@ -50,7 +50,7 @@ type User struct {
 // should be used throughout headscale, in information returned to the
 // user and the Policy engine.
 func (u *User) Username() string {
- return cmp.Or(u.Email, u.Name, u.ProviderIdentifier, fmt.Sprintf("%d", u.ID))
+ return cmp.Or(u.Email, u.Name, u.ProviderIdentifier, strconv.FormatUint(uint64(u.ID), 10))
 }
 
 // DisplayNameOrUsername returns the DisplayName if it exists, otherwise