document all the logical replication types

Signed-off-by: Petros Angelatos <[email protected]>

Author: petrosagg

postgres-protocol/src/replication/mod.rs

@@ -1,16 +1,33 @@
+//! This module defines the [DecodingPlugin] trait that can be used to implement the decoding
+//! logic of any logical decoding plugin.
+//!
+//! Two reference implementations are provided:
+//!
+//! * [PgOutput]: Decodes the built-in pgoutput stream
+//! * [Raw]: A dummy plugin that yield each message it receives as bytes
+
 use std::collections::HashMap;
 
 use crate::message::backend::Parse;
 
+/// Types related to the `pgoutput` plugin type
 pub mod pgoutput;
+/// Types related to the `raw` plugin type
 pub mod raw;
 
 pub use pgoutput::PgOutput;
 pub use raw::Raw;
 
+/// A type that implements this trait can be used as a plugin during logical replication.
+///
+/// The majority of the work is implemented as part of the [Parse] implementation of the associated
+/// type `Message`.
 pub trait DecodingPlugin {
+    /// The type of messages contained into the logical stream
     type Message: Parse;
 
+    /// The name of the plugin
     fn name(&self) -> &str;
+    /// The options the plugin was initialized with
     fn options(&self) -> HashMap<String, String>;
 }