External linking is a complex implementation to be able to serve a clean and easy-to-use interface.
Internally, there are no such things as "external links" (plural). Each Entry in the store can only have one external link.
This library does the following therefor: It allows you to have several external links with one entry, which are internally one file in the store for each link, linked with "internal linking".
This helps us greatly with deduplication of URLs.