feat(auth): add unified auth protocol discovery and optional DPoP support #591

Job	Run time
checks / pre-commit	32s
checks / readme-snippets	11s
checks / test (3.10, locked, ubuntu-latest)	53s
checks / test (3.12, locked, ubuntu-latest)	59s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.10, lowest-direct, windows-latest)	2m 22s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
checks / test (3.11, locked, windows-latest)	2m 26s
checks / test (3.10, locked, windows-latest)	2m 13s
checks / test (3.11, lowest-direct, windows-latest)	3m 0s
checks / test (3.12, locked, windows-latest)	3m 37s
checks / test (3.12, lowest-direct, windows-latest)	3m 40s
checks / test (3.11, lowest-direct, ubuntu-latest)	56s
checks / test (3.11, locked, ubuntu-latest)	47s
checks / test (3.13, lowest-direct, ubuntu-latest)	58s
checks / test (3.14, locked, ubuntu-latest)	2m 26s
checks / test (3.13, locked, ubuntu-latest)	49s
checks / test (3.14, locked, windows-latest)	3m 4s
checks / test (3.13, locked, windows-latest)	2m 38s
checks / test (3.13, lowest-direct, windows-latest)	3m 40s
checks / test (3.14, lowest-direct, windows-latest)	2m 35s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 19s
all-green	4s
	41m 7s

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