Function aligned 

pub(crate) fn aligned(a: &str, b: &str) -> bool

Whether two domains belong together, as DMARC’s relaxed alignment has it: the same, or the same organisational domain (organisational): “mail.example.org”, “shop.example.org” and “example.org” do; “a.github.io” and “github.io” do not, nor “victim.co.uk” and “co.uk”: a name under a public suffix belongs to whoever registered it.