It seems like most people use CDNs for this type of functionality these days, but is there some way to have "site will be back momentarily" sign until all of the nginx-proxy-fed docker services finish starting? This seems like a pretty common use case, so I figured someone here would have a good suggestion or extensions they've written to do this. So if visiting the domain while the services are still coming up - instead of seeing an nginx error (meaningless to most people) - it shows a "please check back in a few moments" message.

I had previous posted this in the wrong project:
nginx-proxy/acme-companion#574