message: Improve comments and add missing documentation
diff: @@ -381,12 +381,16 @@ fn should_stop_fetching(
  true
  }
  +/// Possible errors caused by fetch operation that uses the retry mechanism.
  #[derive(Error, Debug)]
  pub(crate) enum FetchWithRetryError<T>
  where
  T: Item,
  {
  - #[error("Fetch retries exhausted for item with id {id:?}. Total attempts: {total_attempts}, retries while network was connected: {retries_while_connected}")]
  + #[error(
  + "Fetch retries exhausted for item with id {id:?}. Total attempts: {total_attempts}, \
  + retries while network was connected: {retries_while_connected}"
  + )]
  RetriesExhausted {
  id: T::Id,
  total_attempts: usize,
  @@ -397,8 +401,10 @@ where
  FetcherError(#[from] FetcherError<T>),
  }
  -/// Fetches an item. Not suited to fetching a block header or block by height, which require
  -/// verification with finality signatures.
  +/// Fetches an item.
  +///
  +/// Not suited to fetching a block header or block by height, which require verification with
  +/// finality signatures.
  async fn fetch_with_retries<REv, T>(
  ctx: &ChainSyncContext<'_, REv>,
  id: T::Id,
  