[#96] Update Java version from 17 to 21

[HlibYasieniev]

@h1alexbel, please take a look.

PR-Codex Overview

This PR updates the Java version from 17 to 21.

Detailed Summary

• Update Java Version in pom.xml

  • Updated the maven.compiler.source and maven.compiler.target properties to Java 21.
  • Ensured all dependencies are compatible with Java 21.

• Update OpenJDK in Dockerfile

  • Changed the base image from openjdk:17-jdk-alpine to openjdk:21-jdk-alpine.
  • Verified that the application builds and runs correctly with the new Java version in the Docker container.

• *Update Java Version in GitHub Workflows (`.github/workflows/.yml`)**

  • Modified the GitHub Actions workflows to use Java 21.
  • Updated any specific actions or steps that rely on the Java version.

Testing and Verification

• All unit and integration tests have been run and passed.
• Docker image builds successfully and runs without issues.
• GitHub Actions workflows complete successfully using Java 21.

Please review and provide feedback. Thank you!

[h1alexbel]

@YasenevGleb thanks!