Multiuser time-tracker

Task: to develop a backend service Multiuser time-tracker that can be accessed via REST. Time-tracker (Time-tracker or Time-tracking software) is a category of computer software that allows employees working at their computers to record time spent on tasks or projects, and employers to monitor them.

Query types:

1. create a tracking user;
2. change user data;
3. start time-tracking on task X;
4. stop time-tracking on task X;
5. show all time spent by user Y for the period N. .M as a linked list Task - Sum of time spent in the form (hh:mm) sorted from more to less (to answer the question, On which tasks I spent more time);
6. show all time intervals spent working for the period N..M as a linked list Time interval (hh:mm) - Task (to answer the question, What did my week spend on or Where were the 'holes' in the past week when I did nothing);
7. show the sum of labor inputs for all tasks of user Y for the period N..M (as if to display on the Worked this week panel);\
8. clear tracking data of user Z;
9. delete all information about user Z.

CI and maintainability status