Cumulative flow fix
- Fixing bug where the cumulative flow is not showing accurate date.
- Fixing bug where the ticket status history is not sorted.
- Refactoring parts of code where same function is used on both files, so moving the tests as well for effort with the function days_between_dates.
- Refactoring small parts of the code to simplify as suggested by intellisense and linting.
Edited by abhayashrestha