OAuth client: harden SEP-2352/SEP-2350 edge cases; fix conformance co… #2916

Job	Run time
checks / pre-commit	49s
checks / readme-snippets	14s
checks / test (3.12, lowest-direct, windows-latest)	1m 29s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.11, locked, ubuntu-latest)	57s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.11, lowest-direct, windows-latest)	1m 43s
checks / test (3.13, lowest-direct, ubuntu-latest)	58s
checks / test (3.12, locked, ubuntu-latest)	1m 7s
checks / test (3.14, locked, windows-latest)	2m 22s
checks / test (3.10, lowest-direct, windows-latest)	1m 31s
checks / test (3.13, locked, windows-latest)	1m 28s
checks / test (3.12, locked, windows-latest)	1m 48s
checks / test (3.10, locked, windows-latest)	1m 28s
checks / test (3.14, lowest-direct, windows-latest)	1m 34s
checks / test (3.10, locked, ubuntu-latest)	1m 10s
checks / test (3.11, lowest-direct, ubuntu-latest)	59s
checks / test (3.14, locked, ubuntu-latest)	2m 1s
checks / test (3.14, lowest-direct, ubuntu-latest)	57s
checks / test (3.13, locked, ubuntu-latest)	55s
checks / test (3.11, locked, windows-latest)	1m 39s
checks / test (3.13, lowest-direct, windows-latest)	1m 31s
all-green	3s
	28m 54s

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