Persist left-menu pinned state

Relevant code

Add the following API call to toggleLeftMenuPinnedState -> public/js/vue/store/actions.js

There is already a API endpoint for this from the previous left-menus, https://gitlab.com/gitlab-org/gitter/webapp/blob/9faaf438b8ff1df66bbf644ce74044a33ea00db9/public/js/models/room-menu-model.js#L302-307

apiClient.user.put('/settings/leftRoomMenu', { roomMenuIsPinned: false, hasDismissedSuggestions: false }, {
      // No need to get the JSON back from the server...
      dataType: 'text'
    });

Edited Sep 02, 2020 by 🤖 GitLab Bot 🤖