Kargo Expression Language Reference for secret can use global secret

[akolacz]

Checklist

• I've searched the issue queue to verify this is not a duplicate feature request.
• I've pasted the output of kargo version, if applicable.
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Proposed Feature

I would like to have the possibility like global credentials for registry, github etc... to use/reference an global secret with Kargo Expression Language Reference instead of have the same secret in each kargo project.

Motivation

We used in our cases the http promotion to send notifications through slack and we need to setup the bearer token for X kargo project we have, it's for this we would have this secret global and can be used by the Expression Language Reference.

[krancour]

Absolutely can/will do this. Will need to put some thought into the UX. With secrets that come only from within the Project, there's no possibility of name collision, but this would introduce a need for qualifying secrets by namespace when referencing them from within an expression.