What is the role of `google.protobuf.Any` type?

google.protobuf.Any is a special Protobuf well-known type that can contain an arbitrary serialized Protobuf message along with its type URL, providing a form of polymorphism in Protobuf's otherwise strongly-typed system. It is defined as: message Any { string type_url = 1; bytes value = 2; }. The type_url identifies the type (type.googleapis.com/mypackage.MyMessage), and value is the serialized message bytes. Use cases: error details in gRPC error responses (attaching structured error info of varying types), extensible event systems where event payloads vary by event type, and plugin architectures where the schema of plugin data is not known to the host. To use: pack with anypb.New(myMessage) and unpack with anypb.UnmarshalTo(anyValue, &targetMsg, proto.UnmarshalOptions{}). Any sacrifices type safety for flexibility — use sparingly and prefer specific types when possible.