insights: Aggregate code insights results based on user permissions

Created by: coury-clark

Currently the code insights backend runs queries against the internal GraphQL API for the purposes of generating a time-series. This API will return results for all repositories installed on the Sourcegraph instance. The results are recorded in the database, and can be fetched through it's own GraphQL API without filtering based on the user.

Users should only ever be able to know about the repositories that they can have permissions for, including within a code insights aggregate.

More discussion here

Estimated to be completed by: 2021-06-28