Design requirements

1. The rendering of a post needs to be fast. Posts are the core GroupServer, and are used very heavily.
2. The system to display posts needs to be flexible. People can add posts containing any old thing, such as HTML, and plain text.
3. A post may be shown in a number of different contexts:
   • On the Topic page
   • On the Post page
   • On the (rarely visited) Posts page
4. The system needs to handle actions. While the normal thing to do with a post is to read it, people also hide and share posts.
   • Hiding posts needs to be restricted to just the administrator and the author.
   • Sharing should be restricted so people are discouraged from sharing links from private groups with the wider public.