Conversation

@jenniferplusplus In our case, conversation context is a collection of activities. If we add top-level post (Note) to that collection, it becomes a mixed bag. It's harder to parse, and generally doesn't feel right to me.

So I want to have two collections, one with activities and one with posts, and use two different properties:

1. Note.threadContext (or Note.conversationContext) - points to a collection of activities.
2. Note.thread (or Note.context) - points to a collection of posts.

@trwnh @julian