Improved Swagger and OpenAPI documentation

[RadovanTomik]

Negotiator pull request:

Description:

The PR does not modify any bussiness code, it just adds annotations and confiugrations for swagger documentation,

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
• [x] 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 76.84%. Comparing base (9fac93e) to head (6ee3bd7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #277 +/- ## ========================================= Coverage 76.84% 76.84% Complexity 870 870 ========================================= Files 122 122 Lines 2721 2721 Branches 157 157 ========================================= Hits 2091 2091 Misses 524 524 Partials 106 106 ``` | [Flag](https://app.codecov.io/gh/BBMRI-ERIC/negotiator/pull/277/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/277/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BBMRI-ERIC) | `76.84% <ø> (ø)` | | 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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