feat(auth): add unified auth protocol discovery and optional DPoP support #506

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	33s
checks / test (3.10, lowest-direct, ubuntu-latest)	53s
checks / test (3.12, lowest-direct, windows-latest)	3m 33s
checks / test (3.12, locked, ubuntu-latest)	54s
checks / test (3.11, lowest-direct, ubuntu-latest)	58s
checks / test (3.11, locked, windows-latest)	2m 47s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 22s
checks / test (3.10, locked, windows-latest)	2m 17s
checks / test (3.11, lowest-direct, windows-latest)	2m 48s
checks / test (3.11, locked, ubuntu-latest)	49s
checks / test (3.14, lowest-direct, windows-latest)	3m 10s
checks / test (3.13, locked, windows-latest)	2m 30s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 1s
checks / test (3.13, lowest-direct, ubuntu-latest)	52s
checks / test (3.14, locked, windows-latest)	3m 8s
checks / test (3.13, lowest-direct, windows-latest)	3m 2s
checks / test (3.13, locked, ubuntu-latest)	52s
checks / test (3.12, locked, windows-latest)	3m 23s
checks / test (3.14, locked, ubuntu-latest)	2m 20s
checks / test (3.10, lowest-direct, windows-latest)	2m 31s
checks / test (3.10, locked, ubuntu-latest)	54s
all-green	3s
	40m 50s

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