Swagger UI

[lebe1]

Type of change

• [x] New feature (non-breaking change which adds functionality)

Description

This PR adds a Swagger to the backend. It is available via localhost:3000/swagger/ New dependency is swaggo now

Checklist:

• [x] I have commented my code (or ChatGPT did), particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings, neither in my IDE nor in my browser
• [ ] I have added tests that prove my fix is effective or that my feature works

[lebe1]

@nanu-c I will fix that testing error in my next PR when I also change both API calls receiving their data from database