Eager loading

[OluRemiFour]

Close: #1012
All done. Here's a summary of the changes across the two files:
src/dashboard/dashboard.service.ts:83-109
Replaced the eager find({ relations: ['enrollments'] }) with a query builder that:

• LEFT JOINs enrollment on course
• SELECTs course fields + COUNT(enrollment.id) as enrollmentCount
• GROUP BYs course columns
• ORDER BY count descending
• LIMIT 20 via .take(20)
• Returns raw rows (no entity hydration), mapped to the same shape as before
  src/dashboard/dashboard.service.spec.ts
• Updated the Course mock in the shared beforeEach to include createQueryBuilder (needed by exportToCsv → getOverview → getCoursePerformanceMetrics)
• Added a new test 'should compute course performance using aggregate query without hydrating enrollments' that asserts:
• createQueryBuilder('course') is called (not find)
• leftJoin('course.enrollments', 'enrollment') is used
• addSelect('COUNT(enrollment.id)', 'enrollmentCount') is used
• .take(20) limits the result
• orderBy sorts descending by count
• Results are in correct descending order with parsed numeric values
  Index verification
  enrollment.courseId already has a single-column @Index() plus two composite indexes (['courseId', 'status'], ['courseId', 'enrolledAt']). No additional index is needed.

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[OluRemiFour]

Done, Close: #1106

[RUKAYAT-CODER]

Well done on the job done so far!
Kindly fix workflow to pass