getController(request) {
    for (const controllers of [
      this.controllers,
      global.kuzzle.pluginsManager.controllers,
    ]) {
      const controller = controllers.get(request.input.controller);

      if (controller) {
        if (controller._isAction(request.input.action)) {
          return controller;
        }

        throw processError.get(
          "action_not_found",
          request.input.controller,
          request.input.action,
        );
      }
    }

    throw processError.get("controller_not_found", request.input.controller);
  }
Return the controller corresponding to the action asked by the request

@param  {Request} request
@returns {Object} controller object
@throws {BadRequestError} If the asked controller or action is unknown