fix(auth): strip trailing slashes from OAuth metadata URLs #3530

Job	Run time
checks / docs	1m 1s
checks / pre-commit	18s
checks / readme-snippets	12s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 10s
checks / test (3.10, lowest-direct, windows-latest)	1m 58s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 29s
checks / test (3.11, locked, ubuntu-latest)	1m 19s
checks / test (3.13, locked, ubuntu-latest)	1m 17s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 22s
checks / test (3.10, locked, ubuntu-latest)	1m 29s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.11, locked, windows-latest)	1m 30s
checks / test (3.11, lowest-direct, windows-latest)	1m 51s
checks / test (3.12, lowest-direct, windows-latest)	1m 42s
checks / test (3.10, locked, windows-latest)	1m 50s
checks / test (3.12, locked, windows-latest)	1m 44s
checks / test (3.13, locked, windows-latest)	2m 5s
checks / test (3.14, locked, windows-latest)	2m 2s
checks / test (3.14, locked, ubuntu-latest)	1m 26s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 25s
checks / test (3.14, lowest-direct, windows-latest)	1m 51s
checks / test (3.13, lowest-direct, windows-latest)	1m 50s
checks / test (3.12, locked, ubuntu-latest)	1m 5s
all-green	3s
	33m 2s

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