Implement endpoints for the Wikistats2 service.
Unlike the other AQS 2.0 endpoints, these endpoints are Druid-based. There are a relatively large number of them compared to the other AQS 2.0 services, and our partitioning of endpoints into services is somewhat arbitrary. It would not be technically incorrect if, after further consideration, we chose to break Wikistats2 into multiple services. Even if we keep it as one service, we could chose to break endpoint implementation into multiple tasks.
As written, however, this task assumes we will implement all Wikistats2 endpoints in one service, under this task.
Completion criteria: the following endpoints are implemented: