Adds borrow and return actions

The pr adds the borrow and return book actions. I also added check_authorization to make sure every controller authorises the call.
Some parts of the code I use, like the BookKeeper need refactor, but that is not on the scope of this PR.
i believe this might work as well
```
expect(parsed_response.keys).to contain(:started_at, :ends_at, :closed)
```