In order to leverage external domains inside your function(s), you'll need to whitelist them. This can also be done in the Settings section. We have a proxy in place which will check incoming requests from functions and see if the requested URL is whitelisted.
lp-faas-toolbelt, we provide a method that generates the required headers for communication with the proxy. A detailed explanation on how to use this feature is shown here.
Please make sure to whitelist the fully qualified domain name. E.g. If you visit https://liveperson.com the server will actually redirect to https://www.liveperson.com, which means the domains you need to whitelist would be www.liveperson.com and liveperson.com.
Generally, we will prevent the double whitelisting of a domain. The UI will also indicate that this occurred using a dedicated error message. We also perform validation on the provided domain in order to ensure it is a valid domain name. For now, we do not support the whitelisting of subdomains such as .example.com.
Please be aware that it might take up to 5 minutes until the whitelisted domain becomes active on the proxy.