Macro define_plugin 

macro_rules! define_plugin {
    ($plugin_ty:ty, {
        fn new() -> Self $new_body:block

        fn init(&mut self, $ctx_param:ident : &PluginContext $(,)?) -> Result<(), Box<dyn std::error::Error + Send + Sync>> $init_body:block

        fn name(&self) -> &str $name_body:block

        fn version(&self) -> &str $version_body:block

        fn process(
            &self,
            $msg_param:ident : &SpoeMessage $(,)?
        ) -> Result<ProcessingResult, Box<dyn std::error::Error + Send + Sync>> $process_body:block

        $(fn config_schema(&self) -> Option<&str> $schema_body:block)?

        $(fn validate(&self, $vctx_param:ident : &PluginContext $(,)?) -> Vec<Diagnostic> $validate_body:block)?
    }) => { ... };
}