openBinary method
Opens binary content (e.g. a photo body) and returns a handle.
Pair with closeBinary. Consumers should prefer the facade's
openBinaryContent / withBinaryContent helpers, which wrap the
raw handle with a self-closing lifecycle.
Implementation
@override
Future<BinaryContentHandle> openBinary(BinaryRequest request) async {
openBinaryCalls += 1;
binaryRequests.add(request);
return _binaryContentHandle;
}