docs(body): fill in documentation of the to_bytes function

src/body/body.rs

@@ -16,9 +16,10 @@ use crate::upgrade::OnUpgrade;
 
 type BodySender = mpsc::Sender<Result<Bytes, crate::Error>>;
 
-/// A stream of `Bytes`s, used when receiving bodies.
+/// A stream of `Bytes`, used when receiving bodies.
 ///
-/// A good default `Payload` to use in many applications.
+/// A good default [`HttpBody`](crates::body::HttpBody) to use in many
+/// applications.
 #[must_use = "streams do nothing unless polled"]
 pub struct Body {
     kind: Kind,

src/body/to_bytes.rs

@@ -2,7 +2,11 @@ use bytes::{Buf, BufMut, Bytes};
 
 use super::HttpBody;
 
-/// dox
+/// Concatenate the buffers from a body into a single `Bytes` asynchronously.
+///
+/// This may require copying the data into a single buffer. If you don't need
+/// a contiguous buffer, prefer the [`aggregate`](crate::body::aggregate)
+/// function.
 pub async fn to_bytes<T>(body: T) -> Result<Bytes, T::Error>
 where
     T: HttpBody,