feat(auth): add unified auth protocol discovery and optional DPoP support #589

Job	Run time
checks / pre-commit	31s
checks / readme-snippets	10s
checks / test (3.10, lowest-direct, windows-latest)	2m 25s
checks / test (3.13, lowest-direct, ubuntu-latest)	51s
checks / test (3.11, locked, windows-latest)	2m 32s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 19s
checks / test (3.12, locked, ubuntu-latest)	57s
checks / test (3.13, locked, windows-latest)	2m 17s
checks / test (3.12, lowest-direct, ubuntu-latest)	58s
checks / test (3.13, locked, ubuntu-latest)	52s
checks / test (3.10, locked, ubuntu-latest)	51s
checks / test (3.12, locked, windows-latest)	3m 26s
checks / test (3.14, locked, windows-latest)	3m 12s
checks / test (3.12, lowest-direct, windows-latest)	3m 47s
checks / test (3.11, lowest-direct, windows-latest)	2m 40s
checks / test (3.11, lowest-direct, ubuntu-latest)	53s
checks / test (3.10, locked, windows-latest)	2m 21s
checks / test (3.14, locked, ubuntu-latest)	2m 28s
checks / test (3.11, locked, ubuntu-latest)	54s
checks / test (3.14, lowest-direct, windows-latest)	2m 37s
checks / test (3.13, lowest-direct, windows-latest)	2m 40s
all-green	4s
	39m 40s

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