v1.2.3

Changelog:

Both subjects:

• Allow events to be marked as student-only, and do not let teachers book in this case.
• Implement notifications that use the notification content object, and use the tags to decide which users see these notifications.
• Add user ID information to the Assignment Progress CSV files for admin users.
• Allow sending of ADMIN emails from the admin email sending page, which cannot be opted out of.
• Remove unnecessary comments from index HTML files loaded on every fresh page request.
• Neaten Dockefiles to better leverage Docker's build caching.
• Ensure user consistency modal still appears when user changes unexpectedly.
• Accessibility and autofill fixes, ensuring elements have sensible names and labels match.
• Set a genuine domain in the Message-ID of outbound emails, and allow content objects to override the Envelope From address. Simplify the sending functions to reduce the number of parameters.

Physics:

• Implement FastTrack questions and support for the easier/harder questions this entails.
• Add the progress bar for FastTrack questions.

Computer Science:

• Ensure level information is not shown in questions, since current behaviour for levels is physics-specific.
• Alter related content to hide level information and order by difficulty, and only show Related Concepts if any are specified.