fix: Add streaming type re-exports to aws-smithy-legacy-http (#4572)

Author: jlizen

.changelog/1773867889.md

@@ -0,0 +1,13 @@
+---
+applies_to:
+- client
+- aws-sdk-rust
+authors:
+- jlizen
+references:
+- smithy-rs#4431
+breaking: false
+new_feature: false
+bug_fix: true
+---
+Add missing `EventOrInitial`, `EventOrInitialMarshaller`, and `EventStreamSender::into_inner` to `aws-smithy-legacy-http` event_stream module, fixing compilation failures in generated SDKs that reference these types.

rust-runtime/aws-smithy-legacy-http/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aws-smithy-legacy-http"
-version = "0.62.13"
+version = "0.62.14"
 authors = [
     "AWS Rust SDK Team <[email protected]>",
     "Russell Cohen <[email protected]>",
@@ -12,11 +12,12 @@ repository = "https://github.com/smithy-lang/smithy-rs"
 rust-version = "1.91.1"
 
 [features]
-event-stream = ["aws-smithy-eventstream"]
+event-stream = ["aws-smithy-eventstream", "aws-smithy-http/event-stream"]
 rt-tokio = ["aws-smithy-types/rt-tokio"]
 
 [dependencies]
 aws-smithy-eventstream = { path = "../aws-smithy-eventstream", optional = true }
+aws-smithy-http = { path = "../aws-smithy-http", optional = true }
 aws-smithy-runtime-api = { path = "../aws-smithy-runtime-api", features = ["client", "http-02x"] }
 aws-smithy-types = { path = "../aws-smithy-types", features = ["byte-stream-poll-next", "http-body-0-4-x"] }
 bytes = "1.11.1"

rust-runtime/aws-smithy-legacy-http/src/event_stream.rs

@@ -16,5 +16,8 @@ pub type BoxError = Box<dyn StdError + Send + Sync + 'static>;
 #[doc(inline)]
 pub use sender::{EventStreamSender, MessageStreamAdapter, MessageStreamError};
 
+#[doc(inline)]
+pub use aws_smithy_http::event_stream::{EventOrInitial, EventOrInitialMarshaller};
+
 #[doc(inline)]
 pub use receiver::{InitialMessageType, Receiver, ReceiverError};

rust-runtime/aws-smithy-legacy-http/src/event_stream/sender.rs

@@ -47,6 +47,12 @@ impl<T, E: StdError + Send + Sync + 'static> EventStreamSender<T, E> {
     ) -> MessageStreamAdapter<T, E> {
         MessageStreamAdapter::new(marshaller, error_marshaller, signer, self.input_stream)
     }
+
+    /// Extract the inner stream. This is used internally for composing streams.
+    #[doc(hidden)]
+    pub fn into_inner(self) -> Pin<Box<dyn Stream<Item = Result<T, E>> + Send + Sync>> {
+        self.input_stream
+    }
 }
 
 impl<T, E, S> From<S> for EventStreamSender<T, E>