Custom Domains for Plus Subscribers

As a Plus subscriber, I want to point my own custom domain at my Inkwell profile so my journal feels like something I truly own rather than something I rent from a platform. Writers would configure a CNAME record in their DNS provider pointing to Inkwell, then enter the domain in their settings. Their profile page, all entries, and RSS feed would be served from their custom domain (e.g. journal.myname.com) while remaining fully part of the Inkwell network. Inkwell would handle SSL provisioning automatically via Let's Encrypt.