Return untranslated string instead of undefined in runtime translation

[brigadier]

When string is not found in dictionaries it is better to return untranslated string than undefined atom.

[drobakowski]

@brigadier I'm not quite sure if in general it's not better to stick with undefined, as I think that from the point of using the interface it would maybe be helpful for someone to check if a translation was found or not. This change would also break backward compatibility. We also had the need for that and implemented a wrapper around the lookup/3 method:

handle_translation(TextToTranslate) ->
    TPid = boss_web:translator_pid(app_config:app_name()),
    case boss_translator:lookup(TPid, TextToTranslate, <locale>) of
        undefined ->
            TextToTranslate;
        Translation ->
            Translation
    end.

Maybe it would be better to introduce some additional functions for example fun_for_<foo>/2 and for lookup_<foo>/3 which could provide this behaviour and also keep backward compatibility?