I think this is going to depend on how you have deployed the system , as to if you can make some assumptions about the data you’ll receive. Disclaimer, I am speaking from my limited knowledge of the system.
The relationships you’re asking for don’t really exist like that in the UCM.
Directory Numbers themselves are an object that are on their own, and don’t really tether to end users directly except via perhaps the primary extension (set in end user and not necessarily unique) or the directory URI (based on the primary extension for the automatic ones). If the descriptions are templated so they contain some identifying information then you could maybe use that.
Devices can have line appearances of those DNs. Devices can have an owner ID which can be queried directly but not via search or API, which may be set to the user, and thus you can get extensions associated with that user this way. But see above that you won’t know which is theirs if there are multiple unless it matches their primary. There are associated end users with the line appearance for presence which you can get via API, but only through the device. It could also be queried from the DB.
The end user object has everything you want if you deployed everything in place though. The primary extension can be there , obviously user info, and controlled devices , if you populate that. It is not the same as a device owner ID though. If you did that then you can dump end users or use the getuser api , and just parse out the device names in whatever format you need.
It is is a puzzle otherwise and not as easy to piece it together without knowing how things were (or weren’t) deployed.
