feat(api): Implemented session closed and kick event via websocket (#87)

Reviewed-on: #87
Reviewed-by: lq64 <lq@blackhole.local>
Co-authored-by: Janis <janis.e.20@gmx.de>
Co-committed-by: Janis <janis.e.20@gmx.de>

knockoutwhistweb/app/util/mapper/LeftEventMapper.scala

@@ -0,0 +1,19 @@
+package util.mapper
+
+import controllers.routes
+import events.{KickEvent, LeftEvent}
+import model.sessions.UserSession
+import play.api.libs.json.{JsObject, Json}
+
+object LeftEventMapper extends SimpleEventMapper[LeftEvent] {
+
+  override def id: String = "LeftEvent"
+
+  override def toJson(event: LeftEvent, session: UserSession): JsObject = {
+    Json.obj(
+      "url" -> routes.MainMenuController.mainMenu().url,
+      "content" -> views.html.mainmenu.creategame(Some(session.user)).toString
+    )
+  }
+
+}