fix: openai response should contains model (#841)

* 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`

* chore: set model name response for models

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Co-authored-by: JustSong <songquanpeng@foxmail.com>

controller/relay-palm.go

@@ -187,6 +187,7 @@ func palmHandler(c *gin.Context, resp *http.Response, promptTokens int, model st
 		}, nil
 	}
 	fullTextResponse := responsePaLM2OpenAI(&palmResponse)
+	fullTextResponse.Model = model
 	completionTokens := countTokenText(palmResponse.Candidates[0].Content, model)
 	usage := Usage{
 		PromptTokens:     promptTokens,