API information leakage

Ghost User
2017-12-10T21:12:55+01:00

Some private information is leaked from the database through the API.

### Why?
When the ThaliApp requests events information from the website, private information is revealed.
For example, the registration dates of every participant of an event and their member ids.

### Current implementation
When querying the API, data is returned that is private and seemingly unnecessary.

### Desired implementation
The API should only return necessary data.