Profile Activity Ingestion: Move to async processing

[dd32]

Currently the Profile Activity notifier & Badges granting process work interactively with Profiles, which involves a HTTP POST back to ourselves.

This often runs into performance issues, and when we're suffering any database issues compounds the issue.

We should switch this to an async process - where the payload is just added to a queue table which is bulk processed into Profiles.

This would have the downside that activity won't appear instantly, but would also ensure that any activity items aren't missed.

[dd32]

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