Compilation fails if `Default*Pairs` unimplemented in service

### What happened?

A compilation error occured when service does not implement `Default*Pairs`:

```shell
vet: ./generated.go:145:10: result.HasDefaultStoragePairs undefined (type pairStorageNew has no field or method HasDefaultStoragePairs)
```

ref: https://github.com/beyondstorage/go-service-example/runs/3497258311?check_suite_focus=true

### Version

4.7.0
