When in federated mode, back_url is not automatically inserted

[porduna]

In the unmanaged experiments, it is assumed that the client is "redirect". However, in federated environments (including gateway4labs), this is not the case. In these cases, it should automatically provide it, by providing a /finished or similar status and injecting that to back_url if a previous back_url is not already provided.

[porduna]

Fixed