Saml2AuthenticationExceptionMixin doesn't work in JDK 17

[sjohnr]

Saml2AuthenticationExceptionMixin fails when serializing Saml2AuthenticationException on JDK 17, unless the VM option --add-opens java.base/java.lang=ALL-UNNAMED is present.

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Invalid type definition for type `org.springframework.security.saml2.provider.service.authentication.Saml2AuthenticationException`: Failed to call `setAccess()` on Field 'detailMessage' (of class `java.lang.Throwable`) due to `java.lang.reflect.InaccessibleObjectException`, problem: Unable to make field private java.lang.String java.lang.Throwable.detailMessage accessible: module java.base does not "opens java.lang" to unnamed module @5562c41e
 at [Source: (String)"{  "@class": "org.springframework.security.saml2.provider.service.authentication.Saml2AuthenticationException",  "detailMessage": "exceptionMessage",  "error": {    "@class": "org.springframework.security.saml2.core.Saml2Error",    "errorCode": "errorCode",    "description": "errorDescription"  }}"; line: 1, column: 1]
	at app//com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:62)
	at app//com.fasterxml.jackson.databind.DeserializationContext.reportBadTypeDefinition(DeserializationContext.java:1887)
	at app//com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder._handleBadAccess(BeanDeserializerBuilder.java:620)
	at app//com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder._fixAccess(BeanDeserializerBuilder.java:537)
	at app//com.fasterxml.jackson.databind.deser.BeanDeserializerBuilder.build(BeanDeserializerBuilder.java:384)
	at app//com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.buildThrowableDeserializer(BeanDeserializerFactory.java:463)
	at app//com.fasterxml.jackson.databind.deser.BeanDeserializerFactory.createBeanDeserializer(BeanDeserializerFactory.java:113)
	at app//com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer2(DeserializerCache.java:415)
	at app//com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer(DeserializerCache.java:350)
	at app//com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:264)
	at app//com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:244)
	at app//com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:142)
	at app//com.fasterxml.jackson.databind.DeserializationContext.findRootValueDeserializer(DeserializationContext.java:648)
	at app//com.fasterxml.jackson.databind.ObjectMapper._findRootDeserializer(ObjectMapper.java:4861)
	at app//com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4731)
	at app//com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3677)
	at app//com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3645)
	at app//org.springframework.security.saml2.jackson2.Saml2AuthenticationExceptionMixinTests.shouldDeserialize(Saml2AuthenticationExceptionMixinTests.java:53)
        ...

This test began failing when updating the jacoco tool version to 0.8.9. Related gh-13798 and gh-11893. See this comment.

cc @ugrave