Simplify aborting in streams

[neekolas]

Summary

• When you receive a commit from a stream, we need to abort processing the message and sync instead. Previously we did that by decrypting the message and looking at the content to see what kind of message it was.
• There is a better way. There was a private method on the PrivateMessageIn that I have now made public that will let us see what kind of message it is before decrypting.
• This should make streaming more performant and reliable, since we don't have to decrypt the message twice

Related

xmtp/openmls#36

[neekolas]

• Simplify aborting in streams #989 👈
• Refactor process_own_message to not mutate intent state directly #985
• Move staged commit to intents #984 : 1 other dependent PR (#986 )
• main

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[neekolas]

This fix was a bit of a journey. Streaming got fast enough we uncovered a race condition that has been there the whole time. When you add a member to a group and have a stream running there are two syncs that happen. One from the initial add, and one triggered by reading the message from the stream.

If there is a database error like this in the sync originating from the stream, it won't wait to process the message. Then the stream handler will try to look up the message before it has been saved to the DB and return None, making it seem like the message couldn't be processed when in fact it was just processed later.

All this was causing the test_subscribe_membership_changes test to behave flakily.

[neekolas]

Merge activity

• Aug 23, 3:37 PM PDT: @neekolas started a stack merge that includes this pull request via Graphite.
• Aug 23, 3:48 PM PDT: Graphite rebased this pull request as part of a merge.
• Aug 23, 3:53 PM PDT: @neekolas merged this pull request with Graphite.