fix(build): remove Spring Boot 2 Gradle plugin for Gradle 9 compatibility

[adinauer]

📜 Description

Shadow 9.x DuplicatesStrategy fix

Shadow 9.x enforces DuplicatesStrategy before transformers (like mergeServiceFiles and AppendingTransformer) can process duplicates. This means FAIL or EXCLUDE prevents service files and Spring metadata from being merged. All shadow JAR tasks now use DuplicatesStrategy.INCLUDE to let transformers see all duplicate entries.

Spring Boot 2 Gradle plugin removal

Remove the Spring Boot 2 Gradle plugin (org.springframework.boot v2.7.18) which is incompatible with Gradle 9 due to use of removed API LenientConfiguration.getFiles().

Library modules (sentry-spring, sentry-spring-boot, sentry-spring-boot-starter):

• These only used the plugin with apply false to access SpringBootPlugin.BOM_COORDINATES
• Replaced with a direct BOM reference via version catalog (libs.springboot2.bom)

Sample apps (spring-boot, webflux, otel, netflix-dgs):

• Replaced Spring Boot plugin + io.spring.dependency-management with Shadow plugin (com.gradleup.shadow) for fat JAR creation
• Added application plugin for main class configuration
• Uses platform(libs.springboot2.bom) for dependency version management
• Shadow JAR configured with DuplicatesStrategy.INCLUDE + append() to merge Spring metadata files (spring.factories, spring.handlers, spring.schemas, spring-autoconfigure-metadata.properties)
• BootRun task in otel sample replaced with standard JavaExec

OTel agent shadow JAR fix

• sentry-opentelemetry-agent shadowJar switched from DuplicatesStrategy.FAIL to INCLUDE so mergeServiceFiles can merge inst/META-INF/services/ from the upstream OTel agent and the distro libs

System test runner

• Auto-detects shadowJar vs bootJar build task per module
• Fallback HTTP readiness check for shadow JAR apps (actuator web endpoints don't work in flat JARs)

Note: Spring Boot 3 and 4 plugins are unaffected — they are already Gradle 9 compatible.

💡 Motivation and Context

Stacked on top of #5063. The Spring Boot 2.7.x Gradle plugin uses LenientConfiguration.getFiles() which was removed in Gradle 9, causing bootJar and build tasks to fail. Shadow 9.x changed duplicate handling behavior requiring DuplicatesStrategy.INCLUDE for transformer-based merging to work.

💚 How did you test it?

• ./gradlew :sentry-spring:compileJava :sentry-spring-boot:compileJava :sentry-spring-boot-starter:compileJava — passes
• ./gradlew :sentry-spring:test — passes
• All 5 sample shadow JARs build successfully with properly merged spring.factories (170+ lines)
• Sample app starts, serves HTTP, detected as ready by system test runner
• ./gradlew :sentry-opentelemetry:sentry-opentelemetry-agent:shadowJar — passes, service files properly merged
• Verified merged service file contains entries from both upstream OTel agent and distro

📝 Checklist

• No breaking change or entry added to the changelog.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.

🔮 Next steps

Other Gradle 9 compatibility fixes in the parent PR.

#skip-changelog

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

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[sentry]

Sentry Build Distribution

App Name	App ID	Version	Configuration	Install Page
SDK Size	io.sentry.tests.size	8.37.1 (1)	release	Install Build