runtime: propagate request context through adapters

crates/crank-runtime/src/request_context.rs

@@ -0,0 +1,41 @@
+use std::collections::BTreeMap;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct RuntimeRequestContext {
+    pub request_id: String,
+    pub correlation_id: String,
+}
+
+impl RuntimeRequestContext {
+    pub fn new(request_id: impl Into<String>, correlation_id: impl Into<String>) -> Self {
+        Self {
+            request_id: request_id.into(),
+            correlation_id: correlation_id.into(),
+        }
+    }
+
+    pub fn from_request_id(request_id: impl Into<String>) -> Self {
+        let request_id = request_id.into();
+        Self::new(request_id.clone(), request_id)
+    }
+
+    pub fn outbound_headers(&self) -> BTreeMap<String, String> {
+        BTreeMap::from([
+            ("x-request-id".to_owned(), self.request_id.clone()),
+            ("x-correlation-id".to_owned(), self.correlation_id.clone()),
+        ])
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::RuntimeRequestContext;
+
+    #[test]
+    fn uses_request_id_for_default_correlation_id() {
+        let context = RuntimeRequestContext::from_request_id("req_123");
+
+        assert_eq!(context.request_id, "req_123");
+        assert_eq!(context.correlation_id, "req_123");
+    }
+}