deposit: Improve log rendering to at least log the reason behind error codes

We don't have any context when reading the logs (query and status code) be that gunicorn-swh-deposit.service logs or at the end of the line in kibana. That makes investigation hard to debug.

An actionable action: just adding the "reason" (when error code in {4xx,5xx}) would be a sufficient step forward to close this.

I have started to look into that but i don't currently get what's the needed change (deposit code, django, gunicorn, apache, ...)...

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Migrated from T2626 (view on Phabricator)