The backend application will have to call the yhub REST API for some
operations. We want to use a dedicated service to do that. This first
commit introduces the shape of this service, it only does the
configuration for now, calling actions will be implemented later.
The CollaborationService was doing nothing since we started the
migration to yhub, all the code using it is now removed. Also the
`can-edit` endpoint and all the safeguard mechanism relying on the
presence of other users connected to the websocket will not be used
anymore, it will be possible to replace all of this with yhub, so all
this code is also removed.
The settings COLLABORATION_WS_NOT_CONNECTED_READY_ONLY contains a typo.
We don't want to see READY_ONLY but READ_ONLY. This commit fix the typo
and change everywhere in the codebase the settings name.
Manuel Raynaud