Type Alias OnUserMessageCallback 

pub type OnUserMessageCallback = Box<dyn Fn(Arc<dyn InvocationContext>, Content) -> Pin<Box<dyn Future<Output = Result<Option<Content>>> + Send>> + Send + Sync>;

Callback invoked when a user message is received.

Can modify the message content before processing. Return Ok(Some(content)) to replace the message, Ok(None) to keep original.

Aliased Type

pub struct OnUserMessageCallback(/* private fields */);