Add support for configuration of XSLT security

[maths22]

No description provided.

[flavorjones]

@maths22 Thank you for submitting this! And apologies for my slow reply. Will look at it and optimistically would like to ship in v1.11.0 (see milestone).

[flavorjones]

I just rebased this off current main and added an assertion about NotImplementedError to the tests for JRuby.

[flavorjones]

Again, apologies for the long delay in reviewing this and providing feedback.

There are a few things about this PR that I'd like to change:

• naming. Currently Nokogiri uses the word "options" (e.g., ParseOptions, SaveOptions) and this PR introduces two new words for the same concept: "prefs" and "config". I see that the libxslt docs use "prefs" but in the past the places where we've closely mirrored the libxml2 API are generally the parts of the API I regret most. I think we can improve on libxslt's API.
• initial values. It's not clear from this code or the tests what the initial values of these options is, and the setter isn't called by default.
• tests. I'd really like to have some tests exercising each of these libxslt features so we know whether we accidentally break them in a future release. this again is a hard-won lesson from not doing so when implementing ParseOptions or SaveOptions.

If you're not interested in working on this PR, given the long time delay, I understand. But please let me know if you think you'll be able to work on it? Otherwise I'll keep it open and hopefully find time to address some of this feedback.

[maths22]

Sorry for the big delay here. I've just pushed up a new version that I think exposes a more idiomatic ruby API, has more logical defaults, and checks that the underlying library gets all the config params as expected.

(I'm starting to work on getting nokogiri-xmlsec-instructure passing the build inside nokogiri proper, and currently this xmlsec stuff is shoved into that library where it definitely doesn't belong)

[flavorjones]

@maths22 ❤️ ❤️ ❤️ Thanks for tackling this and the nokogiri-xmlsec integration.