Added some java resourses

[DharshiBalasubramaniyam]

Pull Request

Description

I have added some resources for java under programming languages.

• generics
• stream apis
• practical guide to spring boot rest api crud
• practical guide to microservices in springboot
• unit testing in springboot
• Securing springboot applications with JWT

Closes #1487

Type of change

• Adding a new Resource
• Adding a new Category
• Documentation enhancement or fixes
• Website enhancement or fixes

Checklist:

• I read carefully CONTRIBUTING.md
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

Screenshots (if appropriate):

Please add screenshots to help explain your changes.

Additional

[github-actions]

Thank you for submitting your pull request! 🙌 We'll review it as soon as possible. In the meantime, please ensure that your changes align with our CONTRIBUTING.md. If there are any specific instructions or feedback regarding your PR, we'll provide them here. Thanks again for your contribution! 😊