chore: mention collection that could not be found

Makes debugging easier

Author: DrRataplan

src/modules/api.xq

@@ -551,7 +551,7 @@ declare %private function api:get-collection-config($collection as xs:string?) a
  if (empty($git-collection))
  then error((), "git collection not found!")
  else if (empty($collection-config))
- then error((), "collection config not found!")
+ then error((), "collection config " || $git-collection || " not found!")
  else $collection-config
 };