Investigate adding expiries for join codes

[shu8]

I'm implementing the user onboarding and join codes at the moment.

We might want to look into adding some sort of expiry to the code(s) in future, if we have time, so that the codes can't be used to join a department after 24/48/x hours.

[shu8]

Or, we can add a 'view users' functionality for department managers/hospitals/health boards?

need to consider legal issues/GDPR -- do users know that their email will be visible to their 'superiors'?