ExamFee entity model

[bilalmehrban]

• ExamFee Model Setup & Migrations with EF Core
• ExamFee Broker Select By Id function
• ExamFee Broker Select All function
• ExamFee Broker Insert function
• ExamFee Broker Delete function
• ExamFee Broker Update function

[hassanhabib]

@bilalmehrban just a couple of comments.
@viralpandya please take a look at this PR as well when you get a moment.

[viralpandya]

Please add relationship between ExamFee <---> Fee and Exam <--> ExamFee.