fix: Upgrade error handling to errors/v2 package and refactor error messages.

- Refactor error handling using `errors/v2` package for improved error management and formatting
- Implement changes in relay/controller/text.go, controller/channel-test.go, controller/relay.go, common/message/email.go, relay/controller/audio.go, controller/channel-billing.go, relay/controller/helper.go, relay/channel/common.go, relay/channel/minimax/main.go, and common/message/main.go
- Add package imports and update package paths for better code organization
- Replace hardcoded strings with error variables for consistency and readability
- Implement secure methods for generating unique Message-ID
- Improve SMTP handling and authentication in email.go
- Update response handling and error messages for better user experience
- Add constant checks and modify functions based on imageRequest parameters in helper.go
- Use `http.NewRequest` instead of `fmt.Fprint` for improved request handling in relay/channel/common.go
- Update error handling and formatting for better consistency across all files

controller/relay.go

@@ -110,6 +110,7 @@ func shouldRetry(c *gin.Context, statusCode int) error {
 	if statusCode/100 == 2 {
 		return errors.Errorf("status code = %d", statusCode)
 	}
+
 	return nil
 }