Allow notification handlers post-creation temporary registration #480

Job	Run time
build (ubuntu-latest, Debug)	2m 15s
build (macos-latest, Release)	1m 3s
build (windows-latest, Debug)	5m 3s
build (macos-latest, Debug)	1m 26s
build (ubuntu-latest, Release)	2m 10s
build (windows-latest, Release)	4m 9s
publish-coverage / publish-coverage	47s
	16m 53s

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