refactor: Centralize stream handling and helper functions in relay package

relay/channel/palm/relay-palm.go

@@ -9,6 +9,7 @@ import (
 	"one-api/common"
 	"one-api/constant"
 	"one-api/dto"
+	"one-api/relay/helper"
 	"one-api/service"
 )
 
@@ -112,7 +113,7 @@ func palmStreamHandler(c *gin.Context, resp *http.Response) (*dto.OpenAIErrorWit
 		dataChan <- string(jsonResponse)
 		stopChan <- true
 	}()
-	service.SetEventStreamHeaders(c)
+	helper.SetEventStreamHeaders(c)
 	c.Stream(func(w io.Writer) bool {
 		select {
 		case data := <-dataChan: