Let's say I own the domain example.com and host my DNS with the registrar.
I build a site at coolproject.example.com and plan to host everything on digital ocean. I have other content on the domain and don't want to move all my DNS just for this project.
Currently, I can add coolproject.example.com as a domain in DO and update (at my registrar) my NS records for coolproject.example.com to ns(1-3).digitalocean.com.
So far everything works great. Next, I want to host my assets in a Space at cdn.coolproject.example.com.
I add the space and enable CDN, but when I go to select a custom subdomain, coolproject.example.com isn't even in the list!
At this point my only options are to provide my own certificate or move all my DNS to DO even though everything else is working great setup as is.