Also, fix for notifications throttle delay value

It forces programmers to think about errors we are logging and reporting
to the frontend, because they need to contain no sensitive data.

We do that thanks to a new typeclass method for
the `MonadJobStatus` called `noJobHandle`.

Fixes #258

This commit fixes the issue of the "empty Ngrams". The culprit was a bug
in the `arxiv-api` package, which was fixed by:

gargantext/crawlers/arxiv-api!2 (commits)

In a nutshell, due to the fact the relevant `Conduit` was never
completing, it was blocking the `flow` function, which was endlessly
waiting for the last part of the results to arrive.

Hence we were never calling the `flowCorpusUser`, which is the function
responsible for generating the Ngrams.

We need to fix them properly as part of #198.

This reverts merge request !166

JSON should now be better so that the UI can handle it in task async
handler.

JSON should now be better so that the UI can handle it in task async
handler.

This big commit improves the jobs API in a way that now we can
completely abstract away over a JobLog.

This commit also moves the JobHandle into the `Gargantext.Utils.Jobs.Monad` module.

Based on the suggestions in
https://kodimensional.dev/space-leak