backend requirements for feature Live Poll

• Update ws-room.service
  • creator wants to change settings e.g.: 'viewsVisible' or 'title' (see LivepollSessionPatchAPI in src/app/models/livepoll-session.ts of 1121-branch). This is required following features:
    • when creator creates Live Poll: Notify all participants, automatically open Live Poll Dialog.
    • when creator changes settings for an active Live Poll: creator can click on save; Update those settings for all users
    • when creator stops a Live Poll; All participants can't vote anymore

#1121 (closed) is linked to this issue