message: Make fields of SharedMessageIndex public
diff: @@ -138,9 +138,9 @@ impl Default for SharedMessageType {
  #[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
  pub struct SharedMessageIndex {
  /// Types of messages that may be stored in the index.
  - message_types: SharedMessageType,
  + pub message_types: SharedMessageType,
  /// Minimum message size.
  - min_message_size: u32,
  + pub min_message_size: u32,
  }
  /// File space handling strategy.
  