feat(auth): add Authlib-backed OAuth adapter (related to #1240) #1058

Job	Run time
checks / pre-commit	23s
checks / readme-snippets	12s
checks / test (3.11, lowest-direct, ubuntu-latest)	57s
checks / test (3.11, lowest-direct, windows-latest)	2m 36s
checks / test (3.10, locked, windows-latest)	2m 9s
checks / test (3.10, locked, ubuntu-latest)	43s
checks / test (3.10, lowest-direct, windows-latest)	2m 19s
checks / test (3.11, locked, ubuntu-latest)	44s
checks / test (3.11, locked, windows-latest)	2m 23s
checks / test (3.12, lowest-direct, windows-latest)	3m 30s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
checks / test (3.13, lowest-direct, ubuntu-latest)	58s
checks / test (3.13, lowest-direct, windows-latest)	2m 58s
checks / test (3.12, locked, windows-latest)	3m 17s
checks / test (3.12, locked, ubuntu-latest)	48s
checks / test (3.14, locked, ubuntu-latest)	2m 17s
checks / test (3.14, lowest-direct, windows-latest)	2m 31s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 14s
checks / test (3.13, locked, windows-latest)	2m 17s
checks / test (3.13, locked, ubuntu-latest)	41s
checks / test (3.14, locked, windows-latest)	3m 56s
all-green	4s
	38m 55s

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