Is there a generally accepted name of category for this? I searched Amazon for some books on "software extensibilty" or "extending software," but didn't find anything outside of platform-specific books.
Ink and Switch has done a lot of research lately on what they called "malleable software," but that's a new term they invented, and doesn't have much traction.
I wrote this article for my work -- this is type of thing I've talking about: is there a name for the body of work/study around this type of thing?
https://staffbase.com/blog/integration-patterns