Allow multiple folders in `class_package` node registration key #135

Job	Run time
tests (ubuntu-latest, 3.8, complete)	2m 23s
tests (ubuntu-latest, 3.8, only_plotting)	1m 28s
tests (ubuntu-latest, 3.8, only_postgres)	1m 15s
tests (ubuntu-latest, 3.8, only_r)	2m 31s
tests (ubuntu-latest, 3.8, basic)	1m 15s
tests (macos-latest, 3.8, complete)	3m 54s
tests (macos-latest, 3.8, only_plotting)	2m 56s
tests (macos-latest, 3.8, only_postgres)	3m 12s
tests (macos-latest, 3.8, only_r)	3m 33s
tests (macos-latest, 3.8, basic)	3m 35s
build-and-publish	0s
	26m 2s

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