Streaks spec

The streaks system should refresh once a week in line with leaderboards. Across a week, there should be a requirement to perform a certain number of actions, able to be tweaked from the backend. Further, we may wish to implement some kind of "challenge" system, such as using one "location of the day", required for increasing the streak.

Weekly instead of daily

Weekly streaks make more sense as not everyone is on campus every day. Giving people a full week to do these things should increase participation, as everyone has a fair chance to go to campus and do their streak actions for the week. Therefore, the basic "continuation of streak" goal should be easy to do in a day, and we may want to implement "bonus goals" perhaps for extra points.