Improve handling of GitLab origins in Save Code Now requests

The logic for filtering //bad requests// for Save Code Now needs to be improved to handle the fact that GitLab allows subprojects. For example, https://gitlab.inria.fr/solverstack/maphys/maphys/ is a legitimate origin, but it is flagged as invalid by the WebApp for the moment.

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Migrated from T2331 (view on Phabricator)