Function generate 

pub fn generate<T: Service>(
    service: &T,
    emit_package: bool,
    proto_path: &str,
    compile_well_known_types: bool,
    attributes: &Attributes,
    codec: &HashMap<String, String>,
) -> TokenStream

Generate service for Server.

This takes some Service and will generate a TokenStream that contains a public module containing the server service and handler trait.