fix: strip trailing slash from issuer URL in OAuth metadata serialization #1362

Job	Run time
checks / readme-snippets	12s
checks / pre-commit	38s
checks / test (3.11, lowest-direct, windows-latest)	2m 34s
checks / test (3.12, locked, ubuntu-latest)	1m 0s
checks / test (3.12, lowest-direct, windows-latest)	3m 44s
checks / test (3.12, locked, windows-latest)	3m 5s
checks / test (3.13, locked, windows-latest)	2m 17s
checks / test (3.10, locked, ubuntu-latest)	55s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.13, locked, ubuntu-latest)	50s
checks / test (3.11, locked, ubuntu-latest)	49s
checks / test (3.13, lowest-direct, ubuntu-latest)	57s
checks / test (3.11, locked, windows-latest)	2m 39s
checks / test (3.14, lowest-direct, windows-latest)	3m 11s
checks / test (3.13, lowest-direct, windows-latest)	2m 46s
checks / test (3.11, lowest-direct, ubuntu-latest)	57s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 18s
checks / test (3.14, locked, ubuntu-latest)	2m 21s
checks / test (3.10, lowest-direct, windows-latest)	2m 26s
checks / test (3.14, locked, windows-latest)	3m 19s
checks / test (3.10, locked, windows-latest)	2m 23s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 1s
all-green	4s
	40m 28s

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