[BUG] Error when abandoning a negotiation as a researcher

[svituz]

Describe the bug
When a Researcher tries to abandon a negotiation, it gets a 403 forbidden response

How to reproduce

• Create a Request
• Create a Negotiation
• Try to abandon the Negotiation as a Researcher (i.e., PUT /negotiations/{id}/lifecycle/ABANDON)

What happens
The backend returns a 403 Forbidden response

What should happen
The backend should return 204 No Content and the negotiation status should be updated

Notes
The bug is related to the condition in the NegotiationController for methods sendEvent

if (!NegotiatorUserDetailsService.isCurrentlyAuthenticatedUserAdmin()) {
    throw new ResponseStatusException(HttpStatus.FORBIDDEN);
}

Probably, also as Biobanker the user would get a 403 Forbidden