I started reading to find out why Yaml? In it's place I found a great post.
One thing though, I loved the "AUTH-1" numbering and the Yaml breaks that into an Auth section, with "1." subsection which I don't like nearly as much, the codification AUTH-1 is more referenceable/searchable.
Ah, I should have said explicitly or provided an example of in the post;
The tooling expects that you refer to each requirement by full ID e.g.