[Sprint 4] WaitList Test code & it's implementation code

--- NOTE ---
1. Wait List model is added
2. Wait List Manager code added (method - append , get using filter)
3. Test code for append & get is added
4. User's some validation code is added
-- 8.21
5. Test code for delete from WaitList
6. Implementation code for delete from WaitList
i think 'len(website_url)  > 80'  is right.