Add conformance auth server for OAuth server authentication testing #4036

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	30s
checks / test (3.10, lowest-direct, windows-latest)	2m 18s
checks / test (3.10, highest, windows-latest)	3m 9s
checks / test (3.11, lowest-direct, windows-latest)	2m 32s
checks / test (3.11, highest, windows-latest)	3m 7s
checks / test (3.11, lowest-direct, ubuntu-latest)	49s
checks / test (3.12, highest, ubuntu-latest)	49s
checks / test (3.11, highest, ubuntu-latest)	45s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.12, lowest-direct, ubuntu-latest)	51s
checks / test (3.12, lowest-direct, windows-latest)	3m 31s
checks / test (3.13, lowest-direct, windows-latest)	2m 50s
checks / test (3.14, highest, windows-latest)	2m 30s
checks / test (3.10, highest, ubuntu-latest)	47s
checks / test (3.14, highest, ubuntu-latest)	1m 11s
checks / test (3.12, highest, windows-latest)	3m 36s
checks / test (3.10, lowest-direct, ubuntu-latest)	46s
checks / test (3.14, lowest-direct, windows-latest)	2m 19s
checks / test (3.13, highest, windows-latest)	2m 32s
checks / test (3.13, highest, ubuntu-latest)	45s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 7s
	37m 37s

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