Interface ISecureObjectProviderTarget

Minimal structural shape needed from an OPCUASecureObject (an OPCUAServer, an OPCUAClient, or — via install_push_certificate_management — a plain object exposing the same public surface) to install a resolved provider. Kept structural (rather than importing the OPCUASecureObject class type) so callers that only have a duck-typed view — e.g. push certificate management's OPCUAServerPartial — can use it too.