Upgrade to graphql-java 25.0 and Spring Boot 4

[duckki]

This PR upgrades the project to graphql-java to 25.0 and Spring Boot 4.0.2 and updates all dependencies to their latest compatible stable versions.

Major Version Updates

• Spring Boot: 3.3.6 → 4.0.2
• Spring GraphQL: 1.3.3 → 2.0.2
• graphql-java: 22.3 → 25.0

Dependency Updates

• JetBrains Annotations: 24.1.0 → 26.0.1
• JUnit: 5.10.5 → 5.11.4
• Reactor: 3.6.12 → 3.7.4
• Nexus Publish Plugin: Removed

Breaking Changes Fixed

• Updated test schema snapshots for graphql-java 25 SDL output format changes
• Updated package imports for Spring Boot 4 (GraphQlSourceBuilderCustomizer, ObjectMapper)
• Fixed Jackson 3.x namespace change (com.fasterxml → tools.jackson)
• Resolved Spring Boot 4 test infrastructure changes (removed auto-wired WebTestClient, created local factory methods)
• Fixed subscription callback tests to use verifier, not callback URL.

Test Results

• ✅ All 106 tests passing
• ✅ Spotless formatting verified
• ✅ Code coverage requirements met
• ✅ Full build successful

Reviewer Note

Claude performed the heavy lifting. I'm not so familiar with this codebase and certainly not sure if the spring-subscription-callback test updates make sense. Please review the tests thoroughly.

[github-actions]

Apollo Federation Subgraph Compatibility Results

Federation 1 Support	Federation 2 Support
_service 🟢 @key (single) 🟢 @key (multi) 🟢 @key (composite) 🟢 repeatable @key 🟢 @requires 🟢 @provides 🟢 federated tracing 🟢	@link 🟢 @shareable 🟢 @tag 🟢 @override 🟢 @inaccessible 🟢 @composeDirective 🟢 @interfaceObject 🟢

Learn more:

• Apollo Federation Subgraph Specification
• Compatibility Tests

[dariuszkuc]

we could still rely on autoconfig if we add spring-boot-webtestclient test dependency (which is IMHO a little bit cleaner)

[duckki]

@dariuszkuc I reverted the verifier definitions and corrected the header checking code to use containsHeader. But, Claude and I ran into some issues as below.

First, Claude wouldn't get the @Autowired working. So, I kept the change for now.

Second, Claude couldn't fix some of the test failures:

SubscriptionCallbackHandlerTest > heartbeat() FAILED
    org.opentest4j.AssertionFailedError at SubscriptionCallbackHandlerTest.java:205

SubscriptionCallbackHandlerTest > init_failed() FAILED
    org.opentest4j.AssertionFailedError at SubscriptionCallbackHandlerTest.java:157

SubscriptionCallbackHandlerTest > init_successful() FAILED
    org.opentest4j.AssertionFailedError at SubscriptionCallbackHandlerTest.java:104

SubscriptionCallbackHandlerTest > heartbeat_failed() FAILED
    org.opentest4j.AssertionFailedError at SubscriptionCallbackHandlerTest.java:268

A detailed error:

org.opentest4j.AssertionFailedError: expected: <CallbackMessageNext[id=5090dd66-753e-4241-933c-65b3efe12d0a, verifier=http://localhost:62908/callback/5090dd66-753e-4241-933c-65b3efe12d0a, payload={data={counter=1}}]> but was: <CallbackMessageNext[id=5090dd66-753e-4241-933c-65b3efe12d0a, verifier=junit, payload={data={counter=1}}]>
	at app//org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:158)
	at app//org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:139)
	at app//org.junit.jupiter.api.AssertEquals.failNotEqual(AssertEquals.java:201)
	at app//org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:184)
	at app//org.junit.jupiter.api.AssertEquals.assertEquals(AssertEquals.java:179)
	at app//org.junit.jupiter.api.Assertions.assertEquals(Assertions.java:1188)
	at app//com.apollographql.subscription.callback.SubscriptionCallbackHandlerTest.heartbeat(SubscriptionCallbackHandlerTest.java:205)

So, on the line 205 of SubscriptionCallbackHandlerTest.java, the assertion was expecting "junit" (the verifier variable's value), but the data came in like the callback url value. It's unclear to me why the test changed that way.

Do you have any idea?