feat(auth): add Authlib-backed OAuth adapter (related to #1240) #1060

Job	Run time
checks / readme-snippets	14s
checks / pre-commit	31s
checks / test (3.12, locked, windows-latest)	3m 20s
checks / test (3.10, locked, windows-latest)	2m 11s
checks / test (3.11, lowest-direct, ubuntu-latest)	53s
checks / test (3.11, locked, ubuntu-latest)	51s
checks / test (3.10, locked, ubuntu-latest)	54s
checks / test (3.12, locked, ubuntu-latest)	1m 0s
checks / test (3.13, lowest-direct, ubuntu-latest)	58s
checks / test (3.10, lowest-direct, windows-latest)	2m 29s
checks / test (3.10, lowest-direct, ubuntu-latest)	56s
checks / test (3.14, lowest-direct, windows-latest)	2m 45s
checks / test (3.12, lowest-direct, ubuntu-latest)	59s
checks / test (3.13, lowest-direct, windows-latest)	2m 38s
checks / test (3.14, locked, windows-latest)	3m 50s
checks / test (3.11, locked, windows-latest)	2m 53s
checks / test (3.13, locked, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, windows-latest)	3m 36s
checks / test (3.14, locked, ubuntu-latest)	2m 24s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 14s
checks / test (3.13, locked, windows-latest)	2m 25s
checks / test (3.11, lowest-direct, windows-latest)	2m 39s
all-green	2s
	40m 29s

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