Specify source country for http-01 challenge

[schoen]

@JamesLE

Although you mentioned DNS-01 won't work for you, this might be helpful to other readers: one way to use DNS-01, even if you can't programatically update records on your main DNS host, is to delegate the _acme-challenge subdomain(s) (using NS records) to another host or service that does offer an API, for example: GitHub - joohoi/acme-dns: Limited DNS server with RESTful HTTP API to handle ACME DNS challenges easily and securely.

This is a great tip. You can also do this with a CNAME in some cases, right?

Can we maybe make a new page for in Documentation - Let's Encrypt for some form of "I can't allow incoming connections from the whole world"? Maybe especially with the recent changes, some form of this seems to be a pretty frequently-asked question. I'll make a little draft.

Edit: Here's a very basic draft on this issue.