sync: account for reply tombstones

[latter-bolden]

Summary

Reply parsing was throwing in cases where a thread message was deleted: this results in a tombstone, but wasn't accounted for in method type signatures.

While investigating, I discovered that reply deletes don't work at all. We weren't accounting for the different format and the action sheet fires a generic post delete when you try from a thread. The optimistic update would stick however, so it was deceptive.

Another issue that cropped up while working on it: we had a lingering bug from the @aura upgrade. #5342 should resolve this, but we'll need that to land first. That'll block functional review, but be otherwise fine for code review.

Changes

• custom api method for handling reply deletes
• conditionally call this method from deletePost in action module
• add tombstones as a result type in the replies types of the urbit module
• account for that type difference in the serializer

How did I test?

I deleted messages after fixing the API. Confirmed this creates the parse error that we saw breaking sync. Confirmed with the fix, we get no such parse error.

TODO: this is working for group channels, but I'm seeing a type issue with DMs

Risks and impact

• Safe to rollback without consulting PR author? Yes
• Affects important code area:
  • Message sync
  • Channel display

Operational Note

I think we should merge this into develop and then cherrypick onto the 8.0.3 hotfix branch

Fixes TLON-5128

[linear]

TLON-5128 sync: `syncSince` parse failure

[patosullivan]

One question, otherwise LGTM

[jamesacklin]

Please target release/803, I'll open another PR to merge back into develop.