Add initial implementation of walkthrough

[Yubo-Cao]

Closes N/A

Initial implementation of the walkthrough feature. See this Google Drive video for demonstration: https://drive.google.com/file/d/19sUz1XoSjP0UkuhUvKQE-MZjmVASy2ot/view?usp=sharing

The completion of the walkthrough is also tracked through modifying the preferences class.

This refs #12664

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• Change in CHANGELOG.md described in a way that is understandable for the average user (if change is visible to the user)
• Tests created for changes (if applicable)
• Manually tested changed features in running JabRef (always required)
• Screenshots added in PR description (if change is visible to the user)
• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[trag-bot]

Using ArrayList for cleanupTasks is not optimal. Consider using List.of() for creating an empty list, which is more efficient and aligns with JabRef's conventions.

[calixtus]

Should be at least commented.

Suggested change

	private final List<Runnable> cleanupTasks = new ArrayList<>();
	private final List<Runnable> cleanupTasks = new ArrayList<>(); // needs a mutable list

[trag-bot]

The new method 'getWalkthroughPreferences' should not return 'null'. It should use 'java.util.Optional' to handle the absence of a value, ensuring better null safety and avoiding potential null pointer exceptions.

[Siedlerchr]

So far I like the idea.
Discussion points for Friday would be:

• How many steps we want
• Going back one step?
• content of the steps
• Additional steps like adding stuff to groups or creating a new entry or library

[koppor]

This refs #12664 somehow :)

[calixtus]

What does this have to do with the walkthrough? Stay focused on your project. Don't do any side issues that are not related with your project.

[subhramit]

@calixtus I think configuration of a paper directory was the first point in the description of the project statement in the wiki page, and also mentioned in the issue.

That being said, whether or not that should be a part of "this" PR is worth discussing.

[calixtus]

Please separate the prs. One thing is welcome walkthrough, the other is enhancements to welcome tab. And finish one first.

[trag-bot]

The code directly accesses preferences to check walkthrough completion. This logic should be moved to org.jabref.logic to maintain a clean separation between GUI and logic layers.

[trag-bot]

The targetNode field is set to null in the detach method, which can lead to null pointer exceptions if accessed without checks. Consider using Optional to handle absence of a node.

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

[trag-bot]

@trag-bot didn't find any issues in the code! ✅✨

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