Polished README.md for the project. Made sure that the deletion of all private files did not affect the functionality of the frontend.

Deleted all private data. Created only admin profile. Frontend (local) still works with the backend (also local).

Merge branch '11-when-creating-new-associations-and-assocationmemberships-relatedobjectdoesnotexist' into 'develop'

correct validation of admin page

See merge request !4

fix the authentication of news and eventtype

See merge request !2