Non-Create/Listen activities had their associated object field
normalized and fetched, but only to use their `id` field, which is both
slow and redundant. This also failed on Undo activities, which delete
the associated object/activity in database.
Undo activities will now render properly and database loads should
improve ever so slightly.
This fixes a race condition bug where keys could be regenerated
post-federation, causing activities and HTTP signatures from an user to
be dropped due to key differences.
In general, tests that match these criteria can be made async:
- Doesn't use real Cachex.
- Doesn't write to the Config / Application Environment.
- Uses Mock. Using Mox is fine.
- Uses the streamer.
