feat: Reference schema support (#800) #2990

Job	Run time
test_min_deps (macos-latest)	1m 17s
test_min_deps (windows-latest)	1m 2s
Integration Tests (pdm.minimal.lock)	54s
test_min_deps (ubuntu-latest)	44s
Integration Tests (pdm.lock)	55s
test (3.10, windows-latest)	1m 49s
test (3.9, windows-latest)	1m 40s
test (3.9, macos-latest)	1m 19s
test (3.9, ubuntu-latest)	1m 26s
test (3.11, macos-latest)	1m 3s
test (3.10, ubuntu-latest)	1m 27s
test (3.10, macos-latest)	1m 14s
test (3.12, ubuntu-latest)	1m 28s
test (3.11, ubuntu-latest)	1m 20s
test (3.11, windows-latest)	1m 47s
test (3.13, ubuntu-latest)	1m 38s
test (3.13, windows-latest)	1m 39s
test (3.12, windows-latest)	1m 46s
test (3.12, macos-latest)	1m 5s
test (3.13, macos-latest)	56s
Combine & check coverage	13s
	26m 42s

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