Update modules/validation/helpers.go

Co-authored-by: delvh <dev.lh@web.de>

modules/validation/helpers.go

@@ -94,7 +94,7 @@ func IsValidExternalTrackerURLFormat(uri string) bool {
 
 var (
 	validUsernamePattern   = regexp.MustCompile(`^[\da-zA-Z][-.\w]*$`)
-	invalidUsernamePattern = regexp.MustCompile(`[-._]{2,}|[-._]$`)
+	invalidUsernamePattern = regexp.MustCompile(`[-._]{2,}|[-._]$`) // No consecutive or trailing non-alphanumeric chars 
 )
 
 // IsValidUsername checks if username is valid