Allow multiple folders in `class_package` node registration key #136

Job	Run time
tests (ubuntu-latest, 3.8, complete)	2m 10s
tests (ubuntu-latest, 3.8, only_plotting)	1m 49s
tests (ubuntu-latest, 3.8, only_postgres)	1m 14s
tests (ubuntu-latest, 3.8, only_r)	2m 5s
tests (ubuntu-latest, 3.8, basic)	1m 26s
tests (macos-latest, 3.8, complete)	4m 11s
tests (macos-latest, 3.8, only_plotting)	5m 0s
tests (macos-latest, 3.8, only_postgres)	2m 39s
tests (macos-latest, 3.8, only_r)	3m 30s
tests (macos-latest, 3.8, basic)	3m 11s
build-and-publish	0s
	27m 15s

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