Consider random/hashed IDs for user pages and the ability to change the user page root path

[LukasKalbertodt]

One client of ours voiced interest in this feature as they consider disclosing usernames as a security risk, putting Tobira and other of their systems at risk. I have not yet fully grasp the details here.

The idea would be to (if configured that way) either create a random ID for new user pages (like we do for events) or hash the username. As a separate feature, we could allow users to change their user-page ID, basically like a channel ID on youtube, on a first-come-first-serve basis. Though I imagine follow-up complications there: preventing impersonation, giving lecturers higher priority in the user-page ID choice, ...

In any case, not a big priority right now.