#3503 Add xslt.features support

[DenisIstomin]

Related to #3503

[ppalaga]

Thanks, @DenisIstomin this looks quite good!

Except for the inline suggestions, could you please add some test coverage to the test module under integration-tests/xml? Ideally a new XSLT file. If the functions implementations really have to be in a separate jar file, the you can create a new module under /integration-tests-support.

[DenisIstomin]

Thanks @ppalaga, added an integration test for the extension functions.

[ppalaga]

Great work, thanks @DenisIstomin !

I am checking locally, whether I can make loading the functions from the current project work.
FWIW, it works in native mode because the classloader there is flat.

I have sent #3533 to unblock building this and other PRs

[ppalaga]

I am checking locally, whether I can make loading the functions from the current project work.
FWIW, it works in native mode because the classloader there is flat.

I think this is caused by the fact that TransformerFactory class is resolved using a wrong class loader around here in Camel https://github.com/apache/camel/blob/camel-3.15.0/components/camel-xslt/src/main/java/org/apache/camel/component/xslt/XsltEndpoint.java#L372

I'd say this PR is good to go like this with the known limitation.

I have filed a followup issue #3534 for the class loading problem.

[ppalaga]

The CI build should work now. Could you please squash your two commits, rebase on top of the recent master and force-push? - That should re-trigger the CI for this PR.

[ppalaga]

Thanks again, @DenisIstomin !