[CHORE] Stop translating non-user facing error messages

[rix0rrr]

Describe the issue

I'm noticing that we are currently using gettext() everywhere for 30x and 40x error messages (not the ones in the programming UI)

These error messages should never surface to normal users: they are indications of programming errors on our parts, and they are intended for us (programmer adults who speak English). I would say they don't need to be translated. However, by the fact that we put them in gettext(), they now become translation load for all the volunteer translators.

Suggestion

Let's stop using gettext() for programmer-targeted error messages, and just the error message in the source directly?

[Felienne]

Ah good catch @rix0rrr! I agree, we could surely stop translating some of these.

A hardliner could argue that for a user that uses Hedy entirely in non-English, it is weird to see English error messages "leaking out"; thus revealing that the underlying technology is English, but yeah, the underlying technology is English, sooner or later that will be clear.

The only exception I think might be level_invalid? Kids are extremely likely to try if there is a level 100 or 1000 or 202, this is not a thing (like an ajax error) that is caused by a programming error.

The quiz does not show a route url, so kids are not likely to run into errors there too:

[TiBiBa]

Agree! We should only return English for the errors that shouldn't occur in a normal user flow. However, I also agree with @Felienne that all errors with possible user interaction should be translated. I think the main issue here is our handling and validation of requests.

Currently we have several manual checks on the provided JSON to validate if the object is as expected. This is cumbersome, hard to maintain and also introduces some risks (what if we miss a check for one value?). I would propose to use something like JSON schema to easily validate request bodies.