[feature] Read + Write tombstones for deleted Actors (#1005)

* [feature] Read + Write tombstones for deleted Actors

* copyTombstone

* update to use resultcache instead of old ttl cache

Signed-off-by: kim <grufwub@gmail.com>

* update go-cache library to fix result cache capacity / ordering bugs

Signed-off-by: kim <grufwub@gmail.com>

* bump go-cache/v3 to v3.1.6 to fix bugs

Signed-off-by: kim <grufwub@gmail.com>

* switch on status code

* better explain ErrGone reasoning

Signed-off-by: kim <grufwub@gmail.com>
Co-authored-by: kim <grufwub@gmail.com>

internal/federation/federatingprotocol.go

@@ -169,6 +169,13 @@ func (f *federator) AuthenticatePostInbox(ctx context.Context, w http.ResponseWr
 			// if 400, 401, or 403, obey the interface by writing the header and bailing
 			w.WriteHeader(errWithCode.Code())
 			return ctx, false, nil
+		case http.StatusGone:
+			// if the requesting account has gone (http 410) then likely
+			// inbox post was a delete, we can just write 202 and leave,
+			// since we didn't know about the account anyway, so we can't
+			// do any further processing
+			w.WriteHeader(http.StatusAccepted)
+			return ctx, false, nil
 		default:
 			// if not, there's been a proper error
 			return ctx, false, err