fix: openai response should contains model

- Update model attributes in `claudeHandler` for `relay-claude.go`
- Implement model type for fullTextResponse in `relay-gemini.go`
- Add new `Model` field to `OpenAITextResponse` struct in `relay.go`

controller/relay-claude.go

@@ -204,6 +204,7 @@ func claudeHandler(c *gin.Context, resp *http.Response, promptTokens int, model
 		}, nil
 	}
 	fullTextResponse := responseClaude2OpenAI(&claudeResponse)
+	fullTextResponse.Model = model
 	completionTokens := countTokenText(claudeResponse.Completion, model)
 	usage := Usage{
 		PromptTokens:     promptTokens,

controller/relay-gemini.go

@@ -287,6 +287,7 @@ func geminiChatHandler(c *gin.Context, resp *http.Response, promptTokens int, mo
 		}, nil
 	}
 	fullTextResponse := responseGeminiChat2OpenAI(&geminiResponse)
+	fullTextResponse.Model = model
 	completionTokens := countTokenText(geminiResponse.GetResponseText(), model)
 	usage := Usage{
 		PromptTokens:     promptTokens,

controller/relay.go

@@ -206,6 +206,7 @@ type OpenAITextResponseChoice struct {
 
 type OpenAITextResponse struct {
 	Id      string                     `json:"id"`
+	Model   string                     `json:"model,omitempty"`
 	Object  string                     `json:"object"`
 	Created int64                      `json:"created"`
 	Choices []OpenAITextResponseChoice `json:"choices"`