Expose error messages from external geojson sources to users

[tordans]

Related: https://osmus.slack.com/archives/C1QN12RS7/p1739266138581449?thread_ts=1739253195.529849&cid=C1QN12RS7

Use Case
When I create a challenge based on an external GeoJSON, something might go wrong.

The admin/user should see the error message of what went wrong so he can fix it.

For example…

• the api might respond too slow, so a timeout triggers and nothing is done
• the api might respond with > 50k items, so MR stops due to this limit(?)
• the api response might be malformed

[tordans]

Examples: #454 (comment)

[tordans]

Example: I just finished a debugging session that cost me multiple hours TBH.
In the end, the issues was trivial: My API returned Newline-delimited GeoJSON BUT I had a feature per line not a FeatureCollection.

The API and the Web UI did not give any indication on the error.

I finally found an error message, when I used the staging version and uploaded the API response as a file…

Tasks Failed to Build
JsResultException(errors:List((,List(JsonValidationError(List('features' is undefined on object. Available keys are 'type', 'id', 'properties', 'geometry'),List())))))

I did not check if this error message is only on staging. Or if it is because I used the Upload (not the API-URL).

In any case, exposing this error to me as a user would have saved me hours…

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For reference https://osmus.slack.com/archives/C1QN12RS7/p1739531583947219?thread_ts=1739522832.618589&cid=C1QN12RS7

[tordans]

From a feature point of view…
In case it is complex to expose the error message of an API call to the user in the frontend: Sending emails about error messages from deep inside an async task should be an easy way to work around this. Github does the same when builds fail, for example.

[tordans]

I ran into this again today and – again – it took me about an hour or longer to find the issue.

It turns out, I change the API that presents our data and did not update the challenges, yet.
As a result, the when I rebuild the challenges all tasks where gone.

It would be very helpful if the 404 error that the API returned at https://radverkehrsatlas.de/api/maproulette/data/deprecated_cycleway_shared had been exposed in the UI or via email.