document namecheap API allow list / IP whitelist required for traefik acme Let's Enrypt cert

[meonkeys]

Traefik may throw this error: unable to generate a certificate for the domains [example.com *.example.com]: error: one or more domains had a problem:\n[*.example.com] [*.example.com] acme: error presenting token: namecheap: Invalid request IP: 127.0.0.1 [1011150]\n[example.com] [example.com] acme: error presenting token: namecheap: Invalid request IP: 127.0.0.1 [1011150]\n

This is because Namecheap requires you to specify IP addresses that are allowed to make API requests.

See "Whitelisting IP" at https://www.namecheap.com/support/api/intro/

Specify IP addresses at https://ap.www.namecheap.com/settings/tools/apiaccess/whitelisted-ips