Make it easy to add a third-party dependency to an extension

[stianst]

Description

It should be possible to easily add third-party dependency (an dependency that is not already part of the Keycloak distribution) to an extension, and the dependencies should be packaged together with the extension as a single deployable artifact to Keycloak.

Discussion

No response

Motivation

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Details

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[thomasdarimont]

This could be done via maven plaugins and repacking (prefixing) of the packages to avoid conflicts when the same libraries are used by multiple extensions in different versions.

I did this in the past with the

• maven-shade-plugin -> with package renaming
• maven-assembly-plugin -> jar-with-dependencies

[thomasdarimont]

Perhaps we could leverage something like https://github.com/moditect/layrry