add challenge and project leaderboard endpoints

[jschwarz2030]

This PR re-enables project and challenge leaderboards by isolating their services into dedicated api endpoints. The following has been added:

-Top user leaderboard for Challenges -Top user leaderboard for Projects -User ranking in Challenges (if user is not near the top, their ranking will still be shown)

User rankings for projects will not be included in this PR.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud