Client notification support #3612

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	33s
checks / test (3.10, lowest-direct, windows-latest)	1m 59s
checks / test (3.10, highest, windows-latest)	1m 54s
checks / test (3.10, lowest-direct, ubuntu-latest)	45s
checks / test (3.10, highest, ubuntu-latest)	44s
checks / test (3.11, lowest-direct, ubuntu-latest)	47s
checks / test (3.11, highest, windows-latest)	2m 30s
checks / test (3.11, highest, ubuntu-latest)	44s
checks / test (3.13, highest, ubuntu-latest)	48s
checks / test (3.12, lowest-direct, windows-latest)	3m 13s
checks / test (3.12, lowest-direct, ubuntu-latest)	45s
checks / test (3.11, lowest-direct, windows-latest)	2m 17s
checks / test (3.13, lowest-direct, ubuntu-latest)	42s
checks / test (3.13, highest, windows-latest)	2m 16s
checks / test (3.12, highest, windows-latest)	2m 45s
checks / test (3.12, highest, ubuntu-latest)	51s
checks / test (3.13, lowest-direct, windows-latest)	2m 36s
	26m 19s

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