feat(auth): add Authlib-backed OAuth adapter (related to #1240) #1057

Job	Run time
checks / pre-commit	21s
checks / readme-snippets	11s
checks / test (3.10, locked, windows-latest)	2m 11s
checks / test (3.11, locked, windows-latest)	2m 25s
checks / test (3.12, locked, ubuntu-latest)	50s
checks / test (3.10, lowest-direct, ubuntu-latest)	59s
checks / test (3.12, locked, windows-latest)	3m 54s
checks / test (3.11, lowest-direct, ubuntu-latest)	56s
checks / test (3.11, locked, ubuntu-latest)	43s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.12, lowest-direct, windows-latest)	3m 36s
checks / test (3.11, lowest-direct, windows-latest)	3m 4s
checks / test (3.10, locked, ubuntu-latest)	45s
checks / test (3.13, lowest-direct, ubuntu-latest)	55s
checks / test (3.10, lowest-direct, windows-latest)	2m 23s
checks / test (3.13, locked, windows-latest)	2m 23s
checks / test (3.14, locked, ubuntu-latest)	2m 18s
checks / test (3.13, locked, ubuntu-latest)	41s
checks / test (3.14, locked, windows-latest)	3m 2s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 18s
checks / test (3.13, lowest-direct, windows-latest)	2m 43s
checks / test (3.14, lowest-direct, windows-latest)	2m 25s
all-green	5s
	39m 10s

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