adds read_cai test for PDF with content credentials #1703

Job	Run time
Clippy	2m 26s
License / vulnerability audit (advisories)	25s
Preflight docs.rs build	1m 52s
License / vulnerability audit (bans licenses sources)	25s
Enforce Rust code format	12s
Preflight crate publish (ubuntu-latest, stable)	56s
Unit tests with minimum versions of direct dependencies (windows-latest)	5m 1s
Unit tests (windows-latest, stable)	6m 5s
Unit tests with minimum versions of direct dependencies (macos-latest)	6m 42s
Unit tests (aarch64-unknown-linux-gnu, stable)	6m 2s
Unit tests (windows-latest, 1.70.0)	10m 21s
Unit tests with minimum versions of direct dependencies (ubuntu-latest)	2m 38s
Unit tests (aarch64-unknown-linux-gnu, 1.70.0)	6m 29s
Unit tests (WASM)	1m 19s
Unit tests (macos-latest, stable)	6m 8s
Unit tests (macos-latest, 1.70.0)	8m 37s
Unit tests (ubuntu-latest, stable)	3m 54s
Check for unused dependencies	2m 23s
Ensure (MINOR) tag is used when making an API breaking change	2m 45s
Unit tests (ubuntu-latest, 1.70.0)	3m 59s
	1h 18m 39s

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