Added serving of FEP-ef61 portable objects through the gateway endpoint, e.g., GET /.well-known/apgateway/did:key:z6Mk.../notes/123. Existing object dispatchers serve such a request with the path after the DID, so the object dispatcher registered for /notes/{id} serves the portable object ap+ef61://did:key:z6Mk.../notes/123. Fedify responds with 404 Not Found unless the dispatcher returns an object with that ID, and refuses to serve a portable actor, activity, or object that does not have an Object Integrity Proof made with a key of the DID. As FEP-ef61 forbids gateways to serve a non-public object to anyone but its intended audience, and a gateway may store objects that it did not create, Fedify also responds with 404 Not Found unless the object is publicly addressed, i.e., its to, cc, bto, bcc, or audience has the public collection, or is an actor. To serve non-public portable objects to their audience, set an authorization predicate on the object dispatcher, e.g., one that checks the request with the new RequestContext.isSignedByAudience() method; the predicate then decides who may retrieve the dispatcher's portable objects, and Fedify responds to the requests that it allows with Cache-Control: private. Applications that do not serve portable objects are unaffected, except that their object dispatchers may be called for such requests. [[#288], [#835], [#1076], [#1153], [#1183]]

Added the RequestContext.isSignedByAudience() method, which checks whether the request is signed by an actor in the audience of an object, comparing FEP-ef61 portable IDs canonically, and the IsSignedByAudienceOptions interface. Its isMember option checks the members of collections such as followers, which Fedify cannot tell by itself. Custom implementations of the RequestContext interface need to implement the new method. [[#288], [#1153], [#1183]]

Added the Context.getPortableObjectUri() method, which builds the portable ID of an object from its object dispatcher's path and a DID, and the RequestContext.portableRequest property, which tells an object dispatcher the DID and ID of the requested portable object. Custom implementations of the Context interface need to implement the new method. [[#288], [#835], [#1076]]

Added serving of tombstones of FEP-ef61 portable objects and actors through the gateway endpoint with 410 Gone, as for ordinary objects, so that other gateways and consumers can tell a deleted portable object from one that the gateway never stored. A Tombstone that an object dispatcher or the actor dispatcher returns for such a request is served with 410 Gone if its ID is the requested portable ID and it has an Object Integrity Proof made with a key of the DID, and with 404 Not Found if it has no proof. Like other portable objects, a tombstone from an object dispatcher without an authorization predicate needs public addressing to be served. [[#288], [#1113], [#1124], [#1153], [#1183]]