refactor: remove project entities

[jungwire]

Negotiator pull request:

Description:

Remove project entities

Checklist:

Make sure you tick all the boxes bellow if they are true or do not apply:

• I have performed a self review of my code
• My code follows Google Java Code style
• I have made my code as simple as possible
• I have added unit tests and the code coverage has not decreased
• I have updated the documentation in all relevant places

[RadovanTomik]

It also needs a DB migration script

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.03%. Comparing base (c32de8e) to head (76a89a3).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #193      +/-   ##
============================================
+ Coverage     75.88%   76.03%   +0.14%     
+ Complexity      908      887      -21     
============================================
  Files           125      119       -6     
  Lines          2700     2658      -42     
  Branches        155      155              
============================================
- Hits           2049     2021      -28     
+ Misses          541      527      -14     
  Partials        110      110              

Flag	Coverage Δ
unit	76.03% <ø> (+0.14%)	⬆️

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