Admin can approve and reject submissions

[MathyouMB]

As a admin, I should be able to review submissions as either approved or rejected.

Implement the approved and rejected methods. Both should create a row in the reviews table. The status of a review "approve / rejected" should be represented as a enum.

We have not implemented "judges" or admins yet, so do not worry about who can access these methods.

Fill in the create method on this file: app/challenges-platform/services/reviews-service.ts leave the TODO comment (don't worry about that check now)

AC:

• implement approved and rejected
• add jest tests for both