Remove user-owned repositories from GraphQL and client side
Created by: mrnugget
This removes from the GraphQL API and from client-side code:
- user-added repositories
- post-sign-up flow
I got the go-ahead on both of these removals from @ryphil.
Test plan
- Existing tests
- Manual sanity check by running app locally and clicking around user settings
- main dry run: https://buildkite.com/sourcegraph/sourcegraph/builds/171295