[client-v2,jdbc-v2] Adds JPA example to Demo Service

[chernser]

Summary

Adds a simple demonstration of using ClickHouse JDBC driver with JPA.

Checklist

Delete items not relevant to your PR:

• Closes #
• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[Copilot]

Copilot reviewed 8 out of 10 changed files in this pull request and generated 2 comments.

Files not reviewed (2)

• examples/demo-service/build.gradle.kts: Language not supported
• examples/demo-service/src/main/resources/application.properties: Language not supported

Comments suppressed due to low confidence (1)

examples/demo-service/src/main/java/com/clickhouse/demo_service/jpa/ClickHouseStringArrayType.java:37

• [nitpick] Consider renaming the iteration variable 'i' to 'item' for improved clarity.

 for (Object i : (Object[]) array.getArray() ) { 

[Copilot]

The isMutable() method returns false, yet deepCopy() creates a new modifiable ArrayList. Either mark the type as mutable or return an unmodifiable collection to maintain consistency.

[chernser]

isMutable() relates to column of this type and so deepCopy() is not linked here. However you might be correct that column should be treated as mutable.

[chernser]

This should stay false to mark value as immutable just for safety. Wrapping with Collections.unmodifiableList() will add performance overhead.

[Copilot]

Typographical error: 'and example' should be corrected to 'an example'.

Suggested change

	This is and example of a Spring Boot service using ClickHouse client directly and via JPA.
	Example is an application that requires ClickHouse DB running externally. It can be a Docker or
	This is an example of a Spring Boot service using ClickHouse client directly and via JPA.

[chernser]

Will do.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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