Comment 20 for bug 547932

A bit of chat implementation notes:
- Chat allows conversation with users friends and groups where user is a member.
- For friends it show if users are online. Groups doesn't have this indicator. In future versions list of online users will be added.
- Users can enable/disable chat in their profile settings.
- Institution admins can enable/disable chat for institution. This will disable chat (and remove relative settings in user profile) for members of this institution unless they also members of other institutions where chat is enabled. If chat enabled for at least one institution (except "No institution") where user is a member, then chat will be enabled for them.
- No institution also has chat setting which effective only for users who do not participate in any other institution.
- Admins can enable/disable chat site-wide by show/hide chat plugin in Extensions admin page.
- If cookie consent is enabled, chat window displayed on top right corner of browser window. Otherwise it is displayed on bottom right corner.
- Chat stores only session cookie which mahara does when cookie consent is enabled.
- If user during his current session has new message, top menu button will show number of channels (users, groups) that have one or more new messages. So, if user has 2 messages from one group and 5 messages from some user, button will show 2 (because 2 channels)
- When chat window is open and some channel is chosen, others channels will show number of new unread messages.
- Switching to channel shows last 50 messages. If there more messages - they are removed.