Upgrade Spring Boot 2.2.6 -> 3.4.1 (Java 17)

[devin-ai-integration]

Summary

Major version upgrade of the monolith module from Spring Boot 2.2.6.RELEASE to 3.4.1, the latest stable 3.x. This pulls in Spring Framework 6, Hibernate 6.6, and Jakarta EE, all managed transitively via the parent BOM. mvn clean install passes with all 7 existing tests green on Java 17.

monolith/pom.xml

• parent 2.2.6.RELEASE → 3.4.1; java.version 11 → 17
• Added spring-boot-starter-validation (validation is no longer bundled with -web since Boot 2.3, and the entities/DTOs use jakarta.validation constraints)
• org.apache.httpcomponents:httpclient (4.x) → org.apache.httpcomponents.client5:httpclient5 (5.x, version managed by the Boot 3 BOM; the old 4.x artifact is no longer in the BOM)

Jakarta EE namespace migration (javax.* → jakarta.*) across all entities/DTOs:

• javax.persistence.* → jakarta.persistence.*
• javax.validation.* → jakarta.validation.*

Apache HttpClient 4 → 5 in SplitTheMonolithApplication:

-import org.apache.http.impl.client.CloseableHttpClient;
-import org.apache.http.impl.client.HttpClientBuilder;
+import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
+import org.apache.hc.client5.http.impl.classic.HttpClientBuilder;

The RestTemplate bean wiring is unchanged — Spring 6's HttpComponentsClientHttpRequestFactory accepts the HttpClient 5 CloseableHttpClient.

Not needed: no Spring Security config, no spring.factories, no spring.redis.*/spring.elasticsearch.*/Actuator properties to rename. application.properties only contained spring.jpa.open-in-view, server.port, and app-specific keys, all still valid in 3.x.

README technologies line updated to "Java 17, Spring Boot 3.x".

Link to Devin session: https://app.devin.ai/sessions/6e501b21ad1f48b08cd9fe0229179a8f
Requested by: @davidbean-hash

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