Allow time-limited re-enabling of member services by members themselves

[brndd]

Background

At Tampere Hacklab, paying for tilankäyttöoikeus (space access) is done monthly, but we don't want people to treat it like a Netflix subscription where they only pay it when they use the lab, because this would not be financially sustainable. This is an eternal point of confusion to some members. I have thought of a change to Mulysa that could help with this issue.

Change

Add a new setting to subscriptions that allows members to disable and re-enable the subscription themselves, but with a cooldown. The cooldown would start ticking down from the re-enablement of the service. While the service is disabled, the user's paid days towards it should not decrease.

In practice we could use this for the Tilankäyttöoikeus subscription to allow members to take breaks from paying it, but not too frequently. Our administrative policy already is that taking long breaks (exact length undefined) is fine, but currently the board has to handle this manually. With this system, members won't have to contact the board themselves, and we don't have to define an exact length for the break -- they can be of any length so long as a year passes between them.

The cooldown period should of course be configurable per-service.

[brndd]

Possible issue: users could abuse the system by coming back for exactly a month once per year.

While I doubt this would be exploited in reality, it would be nice if there was some way of detecting when this happens. Maybe count the number of times a service is paused, and have a table somewhere in the admin panel that allows sorting users by this number to find pause-happy users.