Added schema for questions_attempt table in question db

Made endpoint to get unattempted question based on this logic:

• return a qn both user1 and user2 have not attempted
• if dont have, check if user1 has unattempted qns, if yes choose that
• if dont have, checj if user2 has unattempted qns, if yes choose that
• if not choose the qn that is least attempted among user1 and user2

Made an endpoint to add a new attempt once users attempt a question