Fix authorization checks in attachment upload

[RadovanTomik]

Negotiator pull request:

Description:

Fix authorization checks in attachment upload.

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

Attention: Patch coverage is 79.16667% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 76.80%. Comparing base (ce1903a) to head (7e174a1).

Files	Patch %	Lines
...i_eric/negotiator/service/DBAttachmentService.java	85.00%	1 Missing and 2 partials :warning:
...iator/api/controller/v3/NegotiationController.java	0.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #267 +/- ## ============================================ - Coverage 78.24% 76.80% -1.45% + Complexity 890 869 -21 ============================================ Files 122 122 Lines 2708 2716 +8 Branches 154 157 +3 ============================================ - Hits 2119 2086 -33 - Misses 490 524 +34 - Partials 99 106 +7 ``` | [Flag](https://app.codecov.io/gh/BBMRI-ERIC/negotiator/pull/267/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/267/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=BBMRI-ERIC) | `76.80% <79.16%> (-1.45%)` | :arrow_down: | 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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