refactor backend controllers

[spencerlepine]

Overview

Refactored the entire backend. Rewrote all controller, routes, and controller helper files. Wrote failing tests, and passed them. Created FLOW charts to redesign the Match Generator Algorithm

Ticket

Trello Ticket: #129 Issue #70 Issue: #72 Issue: #74

Checklist

• [x] remove DATA_KEYS reference
• [x] remove constants folder
• [x] write more unit tests
• [x] rewrite EVERY single controller function
• [x] rewrite EVERY helper function
• [x] write failing tests
• [x] pass all tests

Flow charts