Add rootParentIds option to fit the case when all items contain a valid parentId string

[rrbe]

See #23

[philipstanislaus]

Thanks, left a few comments.

I feel that we should not merge the supplied array with the default, but replace it. Otherwise there is no fine grained control when to throw. What do you think?

[rrbe]

Thanks, left a few comments.

I feel that we should not merge the supplied array with the default, but replace it. Otherwise there is no fine grained control when to throw. What do you think?

These modifications are completed, and I also added test case about the rootParentId options replacement, please check it and see what else needs to be modified

[philipstanislaus]

Thanks, just one more note, please see the comments.

[philipstanislaus]

@rrbe sorry for the very late feedback, I just remembered there were some issues/PR still open here.

I have thought about the architecture a bit again and changed the data type for rootParentIds to an object for better performance.

This should be fine now – I will merge it shortly.

Many thanks for your contribution and sorry again for the delay!