* tell browsers and downstream caches to cache for
`env.BADGE_MAX_AGE_SECONDS`, default 0 for dev
* set Cache-Control: no-cache, no-store, must-revalidate if maxAge=0
* add servertime badge to help with cache header debugging
* if service category is 'debug', exclude from examples
* ignore maxAge GET param if less than `env.BADGE_MAX_AGE_SECONDS`