Haha, I do recount many things on those calls. To put it in writing for posterity:
We intend to allow extension of Event Descriptor ("random keys") without changes to the schema.
But dots-in-keys is disallowed by Mongo. In other systems it may be allowed, but confusing. So we ban it. This is something that could be revisited/relaxed in the future if needed.
Closes #268
Just copies the unit test from bluesky itself.