pub fn generate_default_stubs(mut self, enable: bool) -> Self {
        self.generate_default_stubs = enable;
        self
    }
Enable or disable directing service generation to providing a default implementation for service methods.
When this is false all gRPC methods must be explicitly implemented.
When this is true any unimplemented service methods will return 'unimplemented' gRPC error code.
When this is true all streaming server request RPC types explicitly use tonic::codegen::BoxStream type.

This defaults to `false`.
tonic-build/src/prost.rs