gitserver: create reposstats endpoint
Created by: keegancsmith
We want to compute the total number of bytes for git repos on a gitserver. This commit adds a new endpoint to gitserver for ReposStats. ReposStats currently has a field for total number of bytes of all git repos. In future we could also add other relevant statistics.
We compute the total size of the repositories as part of our janitor jobs. We do this because this can be slow to compute. The janitor jobs are useful infrastructure which periodically run over all repositories on a gitserver.
There are no callers of the client yet. We intend to use this in site pings.
Part of https://github.com/sourcegraph/sourcegraph/issues/13713
Co-authored-by: ᴜɴᴋɴᴡᴏɴ [email protected]