Remove deprecated copilot usage API

Remove references to deprecated `/copilot/usage` API.

* **Deleted files:**
  - `backend/src/controllers/usage.controller.ts`
  - `backend/src/models/usage.model.ts`

* **Modified files:**
  - `backend/src/database.ts`: Remove `Usage` schema setup.
  - `backend/src/routes/index.ts`: Remove route for `/usage`.

---

For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/tweag/github-value?shareId=XXXX-XXXX-XXXX-XXXX).

Author: obscurerichard

backend/src/controllers/usage.controller.ts

@@ -60,28 +60,6 @@ class Database {
       name: String,
       value: {}
     }));
-    mongoose.model('Usage', new mongoose.Schema({
-      org: String,
-      team: String,
-      day: Date,
-      total_suggestions_count: Number,
-      total_acceptances_count: Number,
-      total_lines_suggested: Number,
-      total_lines_accepted: Number,
-      total_active_users: Number,
-      total_chat_acceptances: Number,
-      total_chat_turns: Number,
-      total_active_chat_users: Number,
-      breakdown: [{
-        language: String,
-        editor: String,
-        suggestions_count: Number,
-        acceptances_count: Number,
-        lines_suggested: Number,
-        lines_accepted: Number,
-        active_users: Number
-      }]
-    }));
 
     // Language Schema 📝
     const LanguageSchema = new mongoose.Schema({

backend/src/database.ts

@@ -1,6 +1,5 @@
 import { Router, Request, Response } from 'express';
 import surveyController from '../controllers/survey.controller.js';
-import usageController from '../controllers/usage.controller.js';
 import settingsController from '../controllers/settings.controller.js';
 import setupController from '../controllers/setup.controller.js';
 import SeatsController from '../controllers/seats.controller.js';
@@ -22,8 +21,6 @@ router.put('/survey/:id', surveyController.updateSurvey); // put github survey l
 router.delete('/survey/:id', surveyController.deleteSurvey);
 router.post('/survey/:id/github', surveyController.updateSurveyGitHub);
 
-router.get('/usage', usageController.getUsage);
-
 router.get('/metrics', metricsController.getMetrics);
 router.get('/metrics/totals', metricsController.getMetricsTotals);