RFR: 8371440: jpackage should exit with an error if it finds multiple matching signing certificates

[Alexander Matveev]

On Wed, 19 Nov 2025 23:46:36 GMT, Alexey Semenyuk <asemenyuk at openjdk.org> wrote:

> jpackage will exit with an error if the value of the `--mac-signing-key-user-name` option matches multiple certificates of the same type (app image or installer).
> 
> Previously, jpackage would emit an error that multiple certificates match the value of the `--mac-signing-key-user-name` option, pick the first matching certificate, and keep going.

Looks good.

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Marked as reviewed by almatvee (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28405#pullrequestreview-3485256165