click dependency

[doc-sheet]

Hi!
As far as I can see quart has a single place where click is used.
Maybe it would be better to make such dependency optional?

I understand it would still come from flask, but it is a different topic.

[davidism]

Optional dependencies are not great from a code/maintenance/testing perspective, it makes all that much more complicated. We use it, so we depend on it, and it's already available anyway.