Outbox: Add upgrade script to populate outbox items

[obenland]

Proposed changes:

• Adds activitypub_upgrade event for async upgrades with locking.
• Adds upgrade callbacks to create outbox items for posts and comments.
• Adds custom add_to_outbox function that skips any federation considerations.
• Adds tests for the async upgrade event, and outbox generation callbacks.

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

• Not quite sure yet.

[pfefferle]

The risk here is, that all added items will be queued for federation again and because these are quite a lot, it could cause quite some traffic. I think we have to find a way to add historical data without publishing them.

[obenland]

I was hoping the add_filter( 'pre_schedule_event', '__return_false' ); filter would prevent these federation jobs from being scheduled

[pfefferle]

Oh, haven't seen that. True, but this might be only for the moment they were added... the state of the post will still be "pending for federation", so it will be handled at one time...

[obenland]

da26595 adds a localized version of add_to_outbox() that skips all the federation business

[pfefferle]

Does it make sense to have some of the functions in the collection, instead of the migration?

Should we have dedicated classes for bigger migrations, like for example Activitypub\Migration\Outbox?

[pfefferle]

I think we should use the status to track the process of an item. If an item is added, I would set it to pending and if it was sent to the fediverse, I would change that to publish.

[obenland]

Does it make sense to have some of the functions in the collection, instead of the migration?

Sure, what are you thinking?

Should we have dedicated classes for bigger migrations, like for example Activitypub\Migration\Outbox?

At some point I'd like to suggest renaming Migration to Upgrade to align with Core and free up the namespace for any future content migration work. Not sure we need separate classes for upgrade routines (yet). As a matter of fact, I created activitypub_upgrade to make it more reusable for async upgrades and eventually move the existing async routines over to it (reusing more code).