Add MessageResolver

[megascus]

This is regarding the issue I previously reported on the mailing list here:
https://www.eclipse.org/lists/mvc-dev/msg00108.html

Note: AI was used to assist with this fix.

Summary of Changes

I have modified krazo-thymeleaf to load messages.properties directly from the root of the classpath. The location can be customized using org.eclipse.krazo.thymeleaf.messages.basename.
megascus@9ef7efb#diff-0de5e3301051e2ddac61cc1ea8b2dcdaa84c4a4562197524afd487c89dfd26b2R50-R56

This behavior mimics the default behavior of Thymeleaf when integrated with Spring.
The only difference lies in how the Order is configured:
In Spring's MessageResolver, they overwrite the default StandardMessageResolver by not specifying any Order, and then call StandardMessageResolver internally from within Spring's MessageResolver. However, to avoid any potential licensing issues, I implemented this using a different approach.
https://github.com/thymeleaf/thymeleaf-spring/blob/3.1-master/thymeleaf-spring6/src/main/java/org/thymeleaf/spring6/messageresolver/SpringMessageResolver.java

Additionally, extra messages can now be loaded using CDI:
megascus@9ef7efb#diff-7d895401f3946256e9e81972a7e43f20f1e1f412f3e45f5aca5023a6c86b3cfaR59
megascus@9ef7efb#diff-e4949bcf610db73a23d092f64a98472ef44c99084ee3be2d402f93474f1e89b5

Future Considerations

Ideally, this logic should be integrated into Krazo's core resource access mechanism so that other view engines can access messages in a similar manner. However, I haven't gone that far with this implementation yet.

I would really appreciate it if you could review and merge this PR.

[ivargrimstad]

I updated the Jenkinsfile with the changes in the main branch. Please rebase your branch and see if the job runs

[megascus]

Thanks for the fix. It's working now!

[megascus]

Hi, I noticed that some constants are missing/unextracted.

In core Krazo, properties constants are defined in org.eclipse.krazo.Properties. However, since these are specific to Krazo core, adding extension-specific constants to this class doesn't seem like the best approach.

I would like to adopt one of the following options. Which one would be preferred?

1. Create org.eclipse.krazo.ext.thymeleaf.Properties which extends org.eclipse.krazo.Properties
2. Treat them as part of DefaultTemplateEngine behavior and define them in DefaultTemplateEngineProducer
3. Localize them further, treating them as part of MessageResolver behavior and defining them in DefaultMessageResolverProducer

Personally, I prefer Option 1.

// And I noticed that I should change org.eclipse.krazo.thymeleaf.messages.basename property to org.eclipse.krazo.ext.thymeleaf.messages.basename .
// megascus@9ef7efb#diff-0de5e3301051e2ddac61cc1ea8b2dcdaa84c4a4562197524afd487c89dfd26b2R51