[Admin/Backend] App-wide notifications for booth admin users

[somnisomni]

• Add notification panel in admin layout
• Store read status per admin users
• App update chagelog, maintenance, etc...
• Notification can be added in superadmin page
• Content is in Markdown format – parse in frontend

Notification types

• App update notice
• Fair info changes
• Maintenance
• Known Issues
• Emergency notice
• General notice
• (Unspecified)

New DB schema — Notification

• id int not null primary key auto increment
• title varchar(256) not null
• type enum not null default "unspecified" *see above*
• visibility enum[adminOnly, all] not null default "adminOnly"
• content text not null *markdown text*
• createdDate managed by Sequelize but this will be used in the app too

DB schema alteration — Account

• create readNotificationIds json(array) null

New Backend APIs

• GET /admin/notification ‐ Gets all notifications regardless of read status
• POST /admin/notification – Create a new notification
• GET /admin/notification/:id – Get single notification
• PATCH /admin/notification/:id – Edit an existing notification
• DELETE /admin/notification/:id – Delete an existing notification
• POST /admin/notification/:id/read – Update read status of specified notification by adding notification ID in readNotificationIds of current authenticated account