apiClassName can not be cutomized when modular is true

It seems no option named "apiClassName" for the `generateApi` function, and I also try to set name to 'CustomizedAPI', and add a hook to alter the api class name,

```
hooks: {
onPrepareConfig: (currentConfiguration) => {
return {
...currentConfiguration,
config: {
...currentConfiguration.config,
apiClassName: 'CustomizedAPI'
}
}
},
}
```