doc: Add doc draft with simple example

doc/draft.md

@@ -0,0 +1,22 @@
+# Just Enough Doc
+
+## Rum `simple` example
+
+This example is meant to show basic service-based IMAP server with boitalettres library.
+
+- [Source code](../examples/simple.rs)
+
+```shell
+$ cargo run --example simple
+```
+
+- [Basic python testing script](../scripts/test_imap.py)
+
+```shell
+$ python scripts/test_imap.py
+```
+
+## References
+
+- [`imap-codec`](https://docs.rs/imap-codec): IMAP protocol model+encoder/decoder
+- [`tower`](https://docs.rs/tower): Service-based request handling library

examples/simple.rs

@@ -26,7 +26,7 @@ async fn main() -> eyre::Result<()> {
     });
 
     let server = Server::new(incoming).serve(make_service);
-    let _ = server.await;
+    let _ = server.await?;
 
     Ok(())
 }

src/server/mod.rs

@@ -15,7 +15,9 @@ mod service;
 
 #[derive(Debug, thiserror::Error)]
 pub enum Error<A> {
+    #[error("Error occured when accepting new connections")]
     Accept(#[source] A),
+    #[error("Error occured on service creation")]
     MakeService(#[source] Box<dyn std::error::Error + Send + Sync + 'static>),
 }