Allow connecting to the xwiki websocket from Cristal

Currently, the xwiki websocket connector does not support sending credential information.
Therefore, it only work when the connector is embeded in javascript code running in the XWIki instance where it connected, but not cross domains.
We need to introduce a mechanism to allow connecting to a remote xwiki yjs websocket with proper authentication.
Note: this can also mean changing something in the server-side code.