Automatically Download Unity Editor and Components on Build Server

Hi there! I've got the same question that was asked, and answered, here: https://support.unity3d.com/hc/en-u...-version-of-Unity-into-our-build-environment-

"How Can I Have A Fully Automated Build Process That Can Fetch And Install Any Version Of Unity Into Our Build Environment?"

That answer is a few years old and there are a few problems with the answer provided there:
- Not all of the Unity editor and component download URLs follow that form anymore (e.g. some come from `netstorage.unity3d.com` instead of `download.unity3d.com`)
- I don't know how to derive the `{Changeset}` parameter used in that answer from a Unity version number.

So basically I'm looking for the answer to same question as the one asked and partially answered at that URL, but with more complete information, and up to date for March 2019, and covering beta versions.

Thanks in advance!