Prevent directory traversal in server-supplied filenames #2439

Job	Run time
Rustfmt and clippy	49s
Test (x86_64-unknown-linux-gnu, ubuntu-latest, --features=native-tls)	38s
Test (x86_64-unknown-linux-gnu, ubuntu-latest, --no-default-features --features=native-tls,online...	41s
Test (x86_64-apple-darwin, macos-13, --features=native-tls)	1m 27s
Test (aarch64-apple-darwin, macos-14, --features=native-tls)	52s
Test (x86_64-pc-windows-msvc, windows-latest, --features=native-tls)	1m 33s
Test (x86_64-unknown-linux-musl, ubuntu-latest, true)	1m 14s
Test (aarch64-unknown-linux-musl, ubuntu-latest, true, -- --test-threads=4)	1m 47s
Test (arm-unknown-linux-gnueabihf, ubuntu-latest, true, -- --test-threads=4)	2m 7s
	11m 8s

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