feat(auth): add Authlib-backed OAuth adapter (related to #1240) #1061

Job	Run time
checks / pre-commit	37s
checks / readme-snippets	14s
checks / test (3.11, locked, ubuntu-latest)	50s
checks / test (3.11, lowest-direct, ubuntu-latest)	50s
checks / test (3.10, lowest-direct, ubuntu-latest)	52s
checks / test (3.12, lowest-direct, ubuntu-latest)	55s
checks / test (3.10, locked, ubuntu-latest)	50s
checks / test (3.10, locked, windows-latest)	2m 6s
checks / test (3.12, lowest-direct, windows-latest)	3m 29s
checks / test (3.11, lowest-direct, windows-latest)	2m 48s
checks / test (3.10, lowest-direct, windows-latest)	2m 46s
checks / test (3.12, locked, windows-latest)	3m 15s
checks / test (3.13, locked, ubuntu-latest)	49s
checks / test (3.13, lowest-direct, ubuntu-latest)	51s
checks / test (3.14, locked, ubuntu-latest)	2m 19s
checks / test (3.13, lowest-direct, windows-latest)	2m 41s
checks / test (3.13, locked, windows-latest)	2m 21s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 13s
checks / test (3.11, locked, windows-latest)	4m 4s
checks / test (3.14, lowest-direct, windows-latest)	2m 23s
checks / test (3.14, locked, windows-latest)	3m 11s
checks / test (3.12, locked, ubuntu-latest)	57s
all-green	4s
	40m 25s

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