feat: map OpenAI developer role to Gemini system instructions

relay/channel/gemini/relay-gemini.go

@@ -374,7 +374,7 @@ func CovertOpenAI2Gemini(c *gin.Context, textRequest dto.GeneralOpenAIRequest, i
 	var system_content []string
 	//shouldAddDummyModelMessage := false
 	for _, message := range textRequest.Messages {
-		if message.Role == "system" {
+		if message.Role == "system" || message.Role == "developer" {
 			system_content = append(system_content, message.StringContent())
 			continue
 		} else if message.Role == "tool" || message.Role == "function" {