Track user last activity #33
Description
We should track the user last activity. This should be tracked at the account level.
This will let us
- know who is "active"
- have stats like "active in the last 30 days"
- have a feature later, that will let us users decide to auto-delete an inactive account in the future X months.
This should be tracked at the service level - ie we should have a job that is triggered on every user-facing service to do this.