Improved: code to use defined method instead of writing same code again(#456)

[ymaheshwari1]

Related Issues

Using the same logic again to check for default_billing

closes #456

Short Description of the PR

Used the predefined method instead of writing the conditions again

Screenshots of Visual Changes before/after (if There Are Any)

Pull Request Checklist

• [x] I have updated the Changelog (V1) and mentioned all breaking changes in the public API.
• [ ] I have documented all new public APIs and made changes to existing docs mentioning the parts I've changed so they're up to date.
• [x] I have tested my Pull Request on production build and (to my knowledge) it works without any issues
• [ ] I have followed naming conventions

Upgrade Notes and Changelog

• [x] No upgrade steps required (100% backward compatibility and no breaking changes)
• [x] I've updated the Upgrade notes and Changelog on how to port existing Vue Storefront sites with this new feature

Contribution and Currently Important Rules Acceptance

• [x] I read and followed contribution rules

[ymaheshwari1]

@Fifciu Please review

[ymaheshwari1]

Good idea, thanks. Please solve the conflict in the changelog

Resolved conflicts @Fifciu

[ymaheshwari1]

I see unit tests are not passing. Could you please fix them @ymaheshwari1 ?

Sure

[ymaheshwari1]

I see unit tests are not passing. Could you please fix them @ymaheshwari1 ?

Hi @Fifciu Fixed the failing unit tests, please review

[Fifciu]

Great job @ymaheshwari1 , thank you a lot!