CP3108 Staff Dashboard - Backend Modifications for Avengers Leaderboard

[Wong-ZZ]

Context

This PR is for modifying the backend API to support the Avengers Leaderboard component for the CP3018 Staff Dashboard project.

The Avengers Leaderboard is meant to track the grading progress of each avenger however, the current grading overview only provides the group name of the student who submitted the assessment and not the avenger's name.

Implementation

Added a GET route to provide an overview of each group in the course. The overview contains the id of the group, the group's name and the name of the group's avenger.

Other Information

Corresponding PR to cadet-frontend: PR1069
More info in the wiki: Avengers Leaderboard

[coveralls]

Pull Request Test Coverage Report for Build 2896

• 15 of 20 (75.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 91.624%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/cadet_web/controllers/group_controller.ex	5	10	50.0%

Totals
Change from base Build 2893:	-0.3%
Covered Lines:	1072
Relevant Lines:	1170

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💛 - Coveralls