fix: FluentCheckbox class tag always displayed

[Andras-Csanyi]

Pull Request

📖 Description

v2.1.0 brought the bind-Value to the components using FluentInputBase. As a result class attribute is always added to the generated HTML tag (see example below), which unnecessarily increases the HTML size. This PR brings a fix for that and as a result the class attribute in the HTML tag is displayed only when it has value.

The wrong result

<fluent-checkbox class="" value="" current-value="" current-checked="">
childContent
</fluent-checkbox>

The proper result

<fluent-checkbox value="" current-value="" current-checked="">
childContent
</fluent-checkbox>

🎫 Issues

• no relevant issues

👩‍💻 Reviewer Notes

• Not all the components using FluentInputBase covered by tests yet, so there is still some risk the change in this PR includes a bug. If you think a good idea I'm happy to include the tests into this PR. It might take a week or so.

📑 Test Plan

• the change in the component comes with its testing, but see my previous comments

✅ Checklist

General

• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• I have added a new component
• I have modified an existing component

⏭ Next Steps

• tests for all components using FluentInputBase