v2.3.0

Changelog:

• Allow sorting of assignment results by marks on specific questions, or by totals, on the teacher's Assignment Progress page.
• Add support for a opt-in beta feature; text entry of equations. A new box will appear on symbolic questions for those users who have opted in, letting them type answers to these questions rather than use the equation editor.
• Add differentiation Level 6 and integration Level 3 questions to the filter.
• Only show units from published questions in the random units dropdown on numeric questions where no allowedUnits are specified.
• Allow reopening of WebSockets closed by network issues, and don't log this as a WebSocket error. Add a random delay before reattempting the connection. Also, limit the total number any user can have open to 10 and add support for retrying later in these extra tabs.
• Tweaks to the diagnostics endpoint added recently to report the actual number of users with open WebSockets, not just the number of open sockets.
• Add role to contact form messages to help team better respond.
• Fix a bug loading old gameboards whose creator account had been deleted.
• Fix the site statistics Kafka streams application to process all log events from the begginning of time, including those in an older format.
• Improvements to the content error page to better reflect the old behavior lost when moving to the ETL system.
• Move email preferences into user preferences and add support for new user preferences.
• Update nginx to latest stable version.