Remove test prefix from session id?

[ctreffe]

Currently, alfred still adds a "test" prefix to session ids in test sessions. This does not cause any problems, but technically it is not necessary anymore. Is there any reason to keep a test prefix on both the exp_version and the session_id variables?

[jobrachem]

In the spirit of "there should be one way it is done", I agree in principle that we can remove this prefix in the future. It may lead to users relying on the session ID prefix instead of the version prefix, which is something we do not want. However, backwards compatibility would be much better if we just let it sit there. Maybe, to achieve consistency, we should rather also add a "debug" prefix to session ids in debug mode (if there is no such prefix at the moment).