Add a trailing slash to dashboard links (#29555) (#29573)

Backport #29555

modules/translation/mock.go

@@ -6,7 +6,9 @@ package translation
 import "fmt"
 
 // MockLocale provides a mocked locale without any translations
-type MockLocale struct{}
+type MockLocale struct {
+	Lang, LangName string // these fields are used directly in templates: ctx.Locale.Lang
+}
 
 var _ Locale = (*MockLocale)(nil)