docs: add introduction to fluvio message sizes

rfc/produce-message-size.md

@@ -1,7 +1,16 @@
-# Enhancing Fluvio to Message Sizes
+# Enhancing Fluvio Message Sizes
 
 This RFC proposes modifications to Fluvio's handling of message sizes. 
 
+## Introduction
+
+`batch_size` producer config must not reject large records, just send them directly.
+
+Create a new `max_request_size` producer config that must reject large messages.
+I am using `max_request_size` because Kafka uses `max.request.size` but we can change it to other config name.
+
+Compression sizes should not be used for these producer configs.
+
 ## Proposed Enhancements
 
 1. Handling Larger Messages than Batch Size