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:

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

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/BBMRI-ERIC/negotiator/pull/193/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BBMRI-ERIC) | Coverage Δ | | |---|---|---| | [unit](https://app.codecov.io/gh/BBMRI-ERIC/negotiator/pull/193/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BBMRI-ERIC) | `76.03% <ø> (+0.14%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BBMRI-ERIC#carryforward-flags-in-the-pull-request-comment) to find out more.

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