Upgrade Spring Boot 2.0.2 → 2.7.18 and Java 8 → 11

[devin-ai-integration]

Summary

Upgrades the project from Spring Boot 2.0.2.RELEASE / Java 8 to Spring Boot 2.7.18 / Java 11, including build tool and wrapper updates.

pom.xml: Spring Boot parent → 2.7.18, java.version → 11, removed spring-boot-properties-migrator (1.x→2.x migration aid no longer needed).

build.gradle: Plugin → 2.7.18, sourceCompatibility/targetCompatibility → 11, replaced deprecated baseName/version with archiveBaseName/archiveVersion, migrated compile/testCompile to implementation/testImplementation/runtimeOnly, added spring-boot-starter-jdbc and h2 dependencies to match pom.xml.

gs-spring-boot.iml: LANGUAGE_LEVEL → JDK_11.

H2 compatibility: Spring Boot 2.7 pulls H2 2.x which has breaking SQL syntax changes. Added src/main/resources/application.properties with spring.datasource.url=jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;MODE=LEGACY to maintain backward compatibility with the app's H2 1.x SQL (DROP TABLE ... IF EXISTS, SERIAL type).

Wrappers: Regenerated Maven wrapper (3.3.9 → 3.9.6, script-only mode) and Gradle wrapper (4.6 → 7.6.4). Old Gradle 4.6 could not run on JDK 11.

Both ./mvnw clean package and ./gradlew clean build pass on JDK 11.

Review & Testing Checklist for Human

• Boot the app with ./mvnw spring-boot:run (or ./gradlew bootRun) and verify H2 table creation + JDBC operations succeed in the startup log — the MODE=LEGACY setting is the most critical change to validate at runtime
• Note: Application.java calls an external API (gturnquist-quoters.cfapps.io) at startup that is likely defunct — expect a connection error on boot unrelated to this upgrade. Consider removing or replacing it in a follow-up
• Verify gs-spring-boot.iml includes LANGUAGE_LEVEL="JDK_11" (this file is in the diff but could be easy to miss)

Notes

• The repo has no test suite, so correctness beyond successful compilation relies on manual verification of the running application.
• pom.xml uses <packaging>pom</packaging> which is unusual for a Spring Boot app (it skips JAR packaging in Maven). This is pre-existing and unrelated to this PR.

Link to Devin session: https://app.devin.ai/sessions/cc722fb485634c51a38c9cec3f0761a3
Requested by: @danigrim

[devin-ai-integration]

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