pscanrules: add example alerts to DirectoryBrowsingScanRule

[Giothysham]

Added:

• buildAlert()
• getExampleAlerts()
• shouldReturnExpectedExampleAlert() [Test]

Moved:

• Local variables: server, msg and evidence changed to private static variables
• newAlert() code into buildAlert()

Note: This is my first time contributing as a university student, so thorough examination is advised

Part of zaproxy/zaproxy#6119.

[thc202]

The commit must be signed off: https://github.com/zaproxy/zap-extensions/pull/4537/checks?check_run_id=12567537294

The changelog should be updated: https://github.com/zaproxy/zap-extensions/blob/main/CONTRIBUTING.md

You should run the checks locally (e.g. ./gradlew :aO:pscanrules:check).

[Giothysham]

I'm sorry for all the pushes, I was figuring out how to properly sign it, this should be the working code though. Thanks for the help and I hope I wasn’t too much trouble.

[kingthorin]

No problem. There's always a learning curve, we get it.

[kingthorin]

General question: If the name is differentiated should we also be implementing AlertRefs? (Not necessarily for this PR, but just to clarify things further for zaproxy/zaproxy#7100)

[thc202]

I don't think one implies the other, in this case it's exactly the same problem.

[kingthorin]

Okay, thanks.

[thc202]

Thank you! How would you like to be credited (e.g. name, handle)?
https://www.zaproxy.org/docs/desktop/credits/#zap-extended-team

[Giothysham]

Giothysham is fine, thanks for adding me into that list :D