I've been reading into Activity Pub over the last week, and I don't think this would really be the case, (but I'm happy to be wrong).
For example, if a Gitlab instance posts a Pull Request object over to a Mastodon instance, what is the latter supposed to do with that? presumably it won't have any UI widgets to display the content, and no way of acting on it semantically.
As far as I can tell, Activity Pub is a way of federating instances of the same application, with the same semantics. But on the internet I'm seeing some dialogue which seems to presume that AP would make it possible to federate instances of all sorts of different applications and have them all Just Work™
(Apologies if I've misunderstood your post, I'm kinda rambling at this point)
ActivityPub is a very loose spec, and obviously it doesn't just magically work across random services. You would have to implement support for the specific types of notifications for them to be meaningful. An example of this is PeerTube federation with Mastdon as seen here https://peertube.cpy.re/videos/watch/da2b08d4-a242-4170-b32a...
For example, GitLab projects could publish their activity feed to Mastdon. You could follow it to see what commits they make, issue discussions, and so on. Meanwhile, federating things like pull requests would happen across Git based services. So, if Gogs decides to implement compatible ActivityPub protocol, then it could integrate into the federation of GitLab servers.
For example, if a Gitlab instance posts a Pull Request object over to a Mastodon instance, what is the latter supposed to do with that? presumably it won't have any UI widgets to display the content, and no way of acting on it semantically.
As far as I can tell, Activity Pub is a way of federating instances of the same application, with the same semantics. But on the internet I'm seeing some dialogue which seems to presume that AP would make it possible to federate instances of all sorts of different applications and have them all Just Work™
(Apologies if I've misunderstood your post, I'm kinda rambling at this point)