feat: Handle errors, validate model names, and calculate quota usage (#978)

- Improved error handling in various modules for better stability and responsiveness.
- Optimized code in several files for improved efficiency and readability.
- Enhanced user experience by providing more detailed error responses in the controller.
- Strengthened security by ignoring sensitive files in `.gitignore`.

relay/channel/aiproxy/main.go

@@ -189,5 +189,8 @@ func Handler(c *gin.Context, resp *http.Response) (*openai.ErrorWithStatusCode,
 	c.Writer.Header().Set("Content-Type", "application/json")
 	c.Writer.WriteHeader(resp.StatusCode)
 	_, err = c.Writer.Write(jsonResponse)
+	if err != nil {
+		return openai.ErrorWrapper(err, "write_response_body_failed", http.StatusInternalServerError), nil
+	}
 	return nil, &fullTextResponse.Usage
 }