Capability class Null safety
An unforgeable object that comes back as equal when passed through other isolates.
Sending a capability object to another isolate, and getting it back, will produce an object that is equal to the original. There is no other way to create objects equal to a capability object.
Capabilities can be used as access guards: A remote isolate can send a request for an operation, but it is only allowed if the request contains the correct capability object.
This allows exposing the same interface to multiple clients, but restricting some operations to only those clients that have also been given the corresponding capability.
Capabilities can be used inside a single isolate,
but they have no advantage over
new Object to create a unique object,
and it offers no real security against other code
running in the same isolate.
Create a new unforgeable capability object.