Fix multipart body arrays (#938) #2876

Job	Run time
test_min_deps (macos-latest)	1m 23s
test_min_deps (ubuntu-latest)	56s
test_min_deps (windows-latest)	1m 46s
Integration Tests (pdm.lock)	26s
Integration Tests (pdm.minimal.lock)	26s
test (3.10, ubuntu-latest)	1m 18s
test (3.11, ubuntu-latest)	1m 17s
test (3.12, macos-latest)	49s
test (3.13, ubuntu-latest)	1m 23s
test (3.9, windows-latest)	1m 49s
test (3.11, macos-latest)	1m 11s
test (3.10, windows-latest)	1m 46s
test (3.12, ubuntu-latest)	1m 24s
test (3.9, macos-latest)	1m 17s
test (3.10, macos-latest)	1m 14s
test (3.11, windows-latest)	2m 13s
test (3.13, macos-latest)	53s
test (3.12, windows-latest)	2m 8s
test (3.9, ubuntu-latest)	1m 23s
test (3.13, windows-latest)	1m 50s
Combine & check coverage	14s
	27m 6s

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