feat: add spring-mysql-redis to samples java

[Hermione2408]

Description

This PR introduces a new sample application named spring-mysql-redis to the samples-java repository. The application is a simple to-do list manager that demonstrates the integration of key technologies: Spring Boot, MySQL, and Redis.

Spring Boot: Used as the main framework to build the application, providing a robust and flexible foundation for web applications.
MySQL: Serves as the relational database to store persistent data, such as to-do items.
Redis: Implemented as a caching layer to optimize database access and improve performance by storing frequently accessed data.

Fixes # (issue)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• The application was tested by running locally using Docker containers for MySQL and Redis.
• The functionality was verified by creating, reading, updating, and deleting to-do items, with MySQL handling persistent storage and Redis caching these operations.

Additional Context (Please include any Screenshots/gifs if relevant)

...

Checklist:

• My code follows the style guidelines of this project
• 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
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings
• I have tagged the reviewers in a comment below incase my pull request is ready for a review
• I have signed the commit message to agree to Developer Certificate of Origin (DCO) (to certify that you wrote or otherwise have the right to submit your contribution to the project.) by adding "--signoff" to my git commit command.

[Sarthak160]

Please remove .idea folder and target folder also add in gitignore

[Sarthak160]

LGTM