Upgrade Java version from 17 to 21 (MBA-484)

[devin-ai-integration]

Upgrade Java version from 17 to 21 (MBA-484)

Summary

This PR upgrades the project's Java version from 17 to 21 and resolves a conflicting maven-compiler-plugin configuration.

Changes:

• Updated java.version property from 17 to 21 in pom.xml
• Removed the maven-compiler-plugin configuration block that was incorrectly targeting Java 1.8 (source/target). The Spring Boot 3.3.3 parent POM handles compiler settings appropriately for Java 21.

Scope: This is a deliberately narrow change focused only on the pom.xml configuration. Docker, README, and Kubernetes configs are intentionally NOT updated per task requirements and will be handled in separate tickets.

Review & Testing Checklist for Human

• Verify CI environment has Java 21 available - build may fail if CI is still configured for Java 17
• Confirm the application compiles and runs correctly in a Java 21 environment
• Note: Dockerfile still references Java 17 image - deployment will need a separate update before this can be deployed

Recommended test plan:

1. Pull this branch and run mvn clean install -DskipTests with Java 21 locally
2. If MySQL is available, run full tests with mvn clean install
3. Verify CI passes (may require CI environment update)

Notes

• Compilation verified locally with OpenJDK 21.0.9
• Tests were skipped during local verification due to MySQL database not being available (expected)
• JIRA: MBA-484

Link to Devin run: https://app.devin.ai/sessions/190f0e3c20ed469ab6a4e99bf12de818
Requested by: Jia Wu (jia.wu@cognition.ai) (@jia-cog)

[devin-ai-integration]

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