Add unit test coverage for `delete_user` #14

Job	Run time
unit_tests (3.8)	21s
unit_tests (3.9)	21s
unit_tests (3.10)	25s
unit_tests (3.11)	22s
unit_tests (3.12)	32s
py_build_tests / py_build_tests	10s
py_build_tests / relative_path_tests	5s
	2m 16s

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