Add "X-MKit-Chat-UUID" header support for streaming responses (#22)

Updated CORS configuration to expose the "X-MKit-Chat-UUID" header.
Enhanced the streaming setup to include the chat UUID in response
headers when available, improving traceability and debugging for client
applications.
This pull request includes changes to add support for exposing and
handling a new header, `X-MKit-Chat-UUID`, in the API. The most
important changes include modifying the CORS configuration, updating the
streaming headers setup, and ensuring the new header is included when
available.

Changes to CORS configuration:

*
[`cmd/api.go`](diffhunk://#diff-89cdc96cd44fc55cb509f62f12a3dc4173c8b9dfd81222cdff65f8544577920bL192-R192):
Added `X-MKit-Chat-UUID` to the list of exposed headers in the CORS
configuration.

Updates to streaming headers setup:

*
[`internal/handler/chat.go`](diffhunk://#diff-108d955ddd5c30f9c28f9826b706d910f5308d53e2c9dec9a5d112da5e7b133bL321-R336):
Updated the `setupStreamingHeaders` function to accept an additional
`chatUUID` parameter and set the `X-MKit-Chat-UUID` header if the UUID
is available.
*
[`internal/handler/chat.go`](diffhunk://#diff-108d955ddd5c30f9c28f9826b706d910f5308d53e2c9dec9a5d112da5e7b133bL163-R169):
Modified the `HandleAskStream` function to extract the chat UUID from
the request context and pass it to the `setupStreamingHeaders` function.

Author: shahariaazam

cmd/api.go

@@ -189,7 +189,7 @@ func setupRouter(
 		AllowedOrigins:   []string{"*"},
 		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
 		AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-CSRF-Token"},
-		ExposedHeaders:   []string{"Link"},
+		ExposedHeaders:   []string{"Link", "X-MKit-Chat-UUID"},
 		AllowCredentials: true,
 		MaxAge:           300,
 	}))

internal/handler/chat.go

@@ -160,8 +160,13 @@ func HandleAskStream(mcpClient *mcp.Client, logger *log.Logger, historyStorage g
 		}
 		defer reqCtx.span.End()
 
-		// Setup streaming
-		if err := setupStreamingHeaders(w); err != nil {
+		// Setup streaming headers
+		var chatUUID string
+		if reqCtx.chat != nil {
+			chatUUID = reqCtx.chat.UUID.String()
+		}
+
+		if err := setupStreamingHeaders(w, chatUUID); err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
 		}
@@ -318,12 +323,17 @@ func addUserMessage(
 	return messages, nil
 }
 
-func setupStreamingHeaders(w http.ResponseWriter) error {
+func setupStreamingHeaders(w http.ResponseWriter, chatUUID string) error {
 	w.Header().Set("Content-Type", "application/json")
 	w.Header().Set("X-Content-Type-Options", "nosniff")
 	w.Header().Set("Cache-Control", "no-cache")
 	w.Header().Set("Connection", "keep-alive")
 	w.Header().Set("X-Accel-Buffering", "no")
+
+	if chatUUID != "" {
+		w.Header().Set("X-MKit-Chat-UUID", chatUUID)
+	}
+
 	return nil
 }