build

Be more specific when warning the user about missing identity configs #14662

Job	Run time
Build jj-lib without Git support	42s
build (ubuntu-latest)	4m 25s
cargo-deny (advisories)	22s
build (macos-13)	6m 41s
Check protos	31s
Clippy check	2m 29s
cargo-deny (bans licenses sources)	22s
build (macos-14)	3m 54s
build (windows-latest)	10m 5s
Check that MkDocs can build the docs	21s
Check that MkDocs can build the docs with Poetry 1.8	26s
Check formatting	20s
build (ubuntu-latest, --all-features)	5m 25s
	36m 3s

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