fix: strip trailing slashes from OAuth metadata URLs #291

Job	Run time
checks / pre-commit	36s
checks / readme-snippets	12s
checks / test (3.10, locked, windows-latest)	2m 21s
checks / test (3.12, locked, windows-latest)	3m 15s
checks / test (3.13, lowest-direct, windows-latest)	2m 42s
checks / test (3.14, locked, windows-latest)	3m 10s
checks / test (3.11, lowest-direct, windows-latest)	2m 43s
checks / test (3.10, lowest-direct, ubuntu-latest)	42s
checks / test (3.14, locked, ubuntu-latest)	2m 14s
checks / test (3.11, lowest-direct, ubuntu-latest)	40s
checks / test (3.10, locked, ubuntu-latest)	43s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 13s
checks / test (3.14, lowest-direct, windows-latest)	2m 36s
checks / test (3.10, lowest-direct, windows-latest)	2m 27s
checks / test (3.13, locked, ubuntu-latest)	40s
checks / test (3.12, lowest-direct, windows-latest)	3m 43s
checks / test (3.13, lowest-direct, ubuntu-latest)	43s
checks / test (3.11, locked, windows-latest)	2m 23s
checks / test (3.13, locked, windows-latest)	2m 18s
checks / test (3.12, lowest-direct, ubuntu-latest)	53s
checks / test (3.12, locked, ubuntu-latest)	48s
checks / test (3.11, locked, ubuntu-latest)	42s
all-green	2s
	37m 46s

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