fix: Report duplicate @Bean names on Spring 7 configuration classes even when overriding is allowed (#686)

[imuromtsev]

Purpose

The duplicate @Bean name inspection (#597) stayed silent when spring.main.allow-bean-definition-overriding=true. On Spring Framework 7 that is wrong for a full @Configuration class: ConfigurationClassBeanDefinitionReader.isOverriddenByExistingDefinition (spring-context 7.0.9 :337-342) throws BeanDefinitionOverrideException when the class's @Configuration has enforceUniqueMethods = true (the default) or overriding is disallowed, so the property does not rescue it.

Change

• When the class enforces unique methods and the Spring Framework major is 7 or later, the problem is an error whatever spring.main.allow-bean-definition-overriding says (missing, false, true or unresolvable), with a message that names the Spring 7 rule.
• enforceUniqueMethods is read with merged values, as AnnotatedTypeMetadata.getAnnotationAttributes(Configuration) does: a directly declared @Configuration first, else the first annotation composed with it; a meta-fixed @Configuration(enforceUniqueMethods = false) and an @AliasFor default or use-site value count, in Java and Kotlin.
• A lite class (no @Configuration) and @Configuration(enforceUniqueMethods = false) keep the property rule. When the Spring Framework version cannot be determined and the property is true, the problem is a warning.
• Inspection: two @Bean methods with the same bean name in one configuration class fail Spring Boot startup #597 is not released yet, so its [Unreleased] line now states the Spring 7 rule and ends (#597, #686); the inspection description says the same.

Framework evidence

Probe on real jars, one @Configuration class with @Bean A a() + @Bean("a") A b() (and the same across a class hierarchy):

Class	6.2.19, overriding allowed	7.0.9, overriding allowed
@Configuration	starts	fails
lite (@Component)	starts	starts
@Configuration(enforceUniqueMethods = false)	starts	starts
composed, meta @Configuration(enforceUniqueMethods = false)	starts	starts
composed, @AliasFor to enforceUniqueMethods, default false	starts	starts
composed, same alias, use site unique = true (Java and Kotlin)	starts	fails

With overriding disallowed every case fails on both versions.

Not in this PR

• Duplicate @Bean name inspection reports a startup failure on Spring Framework before 6.2.0 #689: Spring Framework before 6.2.0 never fails for this pattern (it silently keeps one method); the inspection still reports a startup failure there. Stacked next.
• Duplicate @Bean name inspection: inherited collisions, overriding property scope, rename fix #668 items 1 and 4 (inherited collision, navigation to the other declaration).

Verification

• Red commits 900388a (Spring 7 + allowed overriding, unknown version) and bfd59bb (review: every property value on Spring 7, composed enforceUniqueMethods), each red failing on the problem or message assertion; Java and Kotlin twins; Spring 7 via the Boot 4.1 test library, unknown version via a spring-core jar without coordinates.
• After the fixes (ee651bc, d1af96b): 54 tests in the SpringDuplicateBeanName* classes, MetaAnnotationsHolderMergedValues* 45/45.
• All modules (:spring-bootstrap:test --rerun-tasks on d1af96b, fresh JUnit XML): spring-core 2413, spring-web 905 (6 skipped), spring-ai 776, jpa 138, spring-data 140, base 35, aop 6, security 6, initializr 5; 0 failures, 0 errors.

Main only: the inspection (#669) and MergedAnnotationAttributes (#673) are not on the release branches.

Closes #686

[github-actions]

	Tests	Passed ✅	Skipped ⚠️	Failed
JUnit Test Report	4424 ran	4418 passed	6 skipped	0 failed

• View JUnit Test Report