API or dataset with contract holder's entire IT Schedule 70 contract

(Original issue is from @hansvonn)

> Is there an api for items on a GSA schedule per contractor? I found a partial set of data [here](https://catalog.data.gov/dataset/gsa-elibrary-schedules-and-contracts) but am unable to find an api or full set of data.
>
> say it is partial because I expect it would contain a contract holder's full contract.
>
> It appears that the file only contains a portion of the records that are on GSA IT Schedule 70. I can compare a single contract holder and see only a few items in the file whereas on the gsaadvantage site there are thousands for that contract holder.
>
> Is there an endpoint that exposes a contract holder's entire GSA IT Schedule 70 contract? I am looking to integrate our system with GSA and pull a contract holder's on-contract listing. Thank you.