Support for AdsDataHub v1

[MarcelHB]

Hello,

Since we are about to use Google AdsDataHub (ADH), we are in the need to manage some things via API.

We noticed that there is no prebuilt client library for ADH v1 while it looks like just another Google API.

Since this repository is already quite comprehensive in terms of listing what Google API clients can be obtained via Maven packages, why not adding ADH v1?

For the records: We have found a generated client inside of the Java samples on the guide pages of ADH. I just wondered whether I did not find it here yet, so it's also running outside of dependency management.

Thanks!