Use reports where possible

[AA-Turner]

For users with access to reports, loading a report and querying in-memory data may be quicker than iterating through all members in a County (or etc.), and will mean less requests to Compass.

Open points

• Would this be transparent via current endpoints, or at a specific /reports/blah endpoint?
• This optimisation is likely only worth it given a certain number of requests - find out that threshold
• Data storage serverside