Refactor `AttendanceRecord` API endpoint

[aryanprince]

• Better naming instead of returnedData1, returnedData2, etc
• More edge case checking like sending 404 if a student hasn't been enrolled
• More comments explaining each step of the API since it's pretty long and does a lot of stuff
• Check if student already has an AttendanceRecord for the same lectureId first
• Check if student is trying to tap after the lectureEndTime