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A new boolean flag, `--unstable-feature-versions`, will be added to the `version-mapping` subcommand in both `kafka-feature.sh` and `kafka-storage.sh`. When this flag is present, the tool will call `MetadataVersion.fromVersionString()` with the unstableFeatureVersionsEnabled flag set to true, allowing users to see feature mappings for development and testing versions. By default (without the flag), only production/stable metadata versions will be included.

Excluding unstable feature versions is the behavior before KAFKA-19544, so this is not a breaking change and can be introduced in 4.x.

New and Changed Public Interfaces

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