Hey, we ar on our way to implement federated stars. We created a test instance to show the new feature - an now you can test federation live :-)

1. The repo ready to receive your star is located at: https://federated-repo.prod.meissa.de/me/star-me
2. Post a star activity at: https://federated-repo.prod.meissa.de/api/swagger#/activitypub/activitypubRepository & press the `Try It Out`` button. The input can look like:
   
3. Put "1" in to the repo & add the following payload

       {
         "id": "https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/1/outbox/12",
         "type": "Star",
         "source": "forgejo",
         "actor": "https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/14",
         "object": "https://federated-repo.prod.meissa.de/api/v1/activitypub/repository-id/1"
       }
       

4. As every user can only put one star, we created 12 users for your experiment on our instance "actor": "https://federated-repo.prod.meissa.de/api/v1/activitypub/user-id/2-13",. But if you are on a forgejo instance having active activitypub/user-id api you can insert also your foreign-instance-user-uri here.
5. Press execute & visit again the repo (https://federated-repo.prod.meissa.de/me/star-me) and enjoy your star :-)
   

At the moment we discuss threats arising by this feature. If you are interested we will be happy to get your 2 cents here: https://codeberg.org/forgejo/forgejo/issues/1854