Add collection:truncate

[y-abs]

What does this PR do ?

This PR implements the collection:truncate method with its unit tests.

How should this be manually tested?

Clone this branch and run unit tests
./gradlew test

When it succeed, compile it

./gradlew jar

Initiate another java project by adding the compiled SDK as a dependency.

Then, run Kuzzle, create an index nyc-open-data, a yellow-taxi collection with several documents in it.
Finally, run this code

import io.kuzzle.sdk.*;
import io.kuzzle.sdk.Options.KuzzleOptions;
import io.kuzzle.sdk.Options.Protocol.WebSocketOptions;
import io.kuzzle.sdk.Protocol.WebSocket;

import java.util.concurrent.ConcurrentHashMap;

public class truncateCollection {
    private static Kuzzle kuzzle;

    public static void main(String[] args) {
        WebSocketOptions opts = new WebSocketOptions();
        opts.setAutoReconnect(true).setConnectionTimeout(42000);

        try {
            WebSocket ws = new WebSocket("localhost", opts);

            kuzzle = new Kuzzle(ws, (KuzzleOptions) null);

            kuzzle.connect();

            kuzzle.getCollectionController().truncate("nyc-open-data", "yellow-taxi").get();
            
        }  catch (Exception e) {
            e.printStackTrace();
        }

        kuzzle.disconnect();
    }
};

[Aschen]

IMHO, you can return nothing

[y-abs]

The API returns it
https://docs.kuzzle.io/core/2/api/controllers/collection/truncate/

[Aschen]

Yes but it's useless IMHO

[scottinet]

The API returns an acknowledgement. This is a way of saying: "the query has been accepted and it ran fine, but there is no result to return".

So, in a SDK, this is a same than a function returning normally. Bothering with creating a ConcurrentHashMap just to return an acknowledgement has no point.

[scottinet]

And to me, this warrants a "requested change", so I'm going to block this PR over this issue.

[scottinet]

API acknowledgements are not return values.

[scottinet]

This dependency seems unused