Front : create class to connect, send and receive message

- Create environment class
 - Create Connexion class to connect and save data
 - Refactor back api

back/src/Model/Websocket/MessageUserPosition.ts

@@ -6,7 +6,7 @@ export class Point implements PointInterface{
     y: number;
 
     constructor(x : number, y : number) {
-        if(!x || !y){
+        if(x === null || y === null){
             throw Error("position x and y cannot be null");
         }
         this.x = x;