refactor: Eliminate Optional from fields and parameters for async method invocation

[guqing]

What this PR does?

Eliminate Optional from fields and parameters

This commit addresses the misuse of the Optional class within our Async Method Invocation pattern. Following #2829 , we have removed Optional from being used as class fields and method parameters.

Key Changes:

• Class fields previously typed as Optional have been converted to nullable types, with added documentation comments to indicate potential nullability.
• Method parameters that were Optional have been refactored.Removed Optional<Exception> from the onComplete method parameter of AsyncCallback and added an additional onError(Exception) method to call when an exception occurs

Rationale:

• Enhances serialization compatibility by removing non-serializable Optional fields.
• Reduces code complexity and improves readability by eliminating the ambiguity of Optional fields and parameters.
• Decreases performance overhead associated with the unnecessary object creation of Optional wrappers.

Fixes #2829

[guqing]

Hi @iluwatar After extensive research, I have been unable to find suitable software to edit the file located at https://github.com/iluwatar/java-design-patterns/blob/master/async-method-invocation/etc/async-method-invocation.ucls and https://github.com/iluwatar/java-design-patterns/blob/master/async-method-invocation/etc/async-method-invocation.png . Following the issue in https://github.com/iluwatar/java-design-patterns/issues/2532, I attempted to download Eclipse and ObjectAid, yet these efforts were unsuccessful🫣. Could you please advise on how I should proceed?😅

[sonarcloud[bot]]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
86.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[iluwatar]

Hi @iluwatar After extensive research, I have been unable to find suitable software to edit the file located at https://github.com/iluwatar/java-design-patterns/blob/master/async-method-invocation/etc/async-method-invocation.ucls and https://github.com/iluwatar/java-design-patterns/blob/master/async-method-invocation/etc/async-method-invocation.png . Following the issue in #2532, I attempted to download Eclipse and ObjectAid, yet these efforts were unsuccessful🫣. Could you please advise on how I should proceed?😅

Hey, don't worry about the .ucls-file. It is a duplicate since we primarily use .urm.puml files that are autogenerated. I'll remove the .ucls-file.

[iluwatar]

Looks good! Thank you for the contribution 🎉

@all-contributors please add @guqing for code

[allcontributors[bot]]

@iluwatar

I couldn't determine any contributions to add, did you specify any contributions? Please make sure to use valid contribution names.

I've put up a pull request to add @guqing! :tada: