We finally published a documentation page about module functions. We call them like that now since we think the old name (functor) is not as descriptive.
Thank you @joshderochervlk!
NOTE: You will still have a better developer experience if you refrain from using them as much as possible! As well as all other advanced features which are listed in the docs sidebar.
But we documented them for the sake of completeness.
Btw: Don’t try to write the word functor without backticks here 