GH-1831: Add auto-truncation support strategies when batching documents

[sobychacko]

Fixes: #1831

• Document auto-truncation configuration with high token limits
• Add integration tests for auto-truncation behavior
• Include Spring Boot and manual configuration examples
• Test large documents and batching scenarios

Enables proper use of embedding model auto-truncation while avoiding batching strategy exceptions.

[markpollack]

I see test errors.

org.opentest4j.AssertionFailedError: Unexpected exception thrown: java.lang.IllegalArgumentException: Tokens in a single document exceeds the maximum number of allowed input tokens

	at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:152)
	at org.junit.jupiter.api.AssertDoesNotThrow.createAssertionFailedError(AssertDoesNotThrow.java:84)
	at org.junit.jupiter.api.AssertDoesNotThrow.assertDoesNotThrow(AssertDoesNotThrow.java:53)
	at org.junit.jupiter.api.AssertDoesNotThrow.assertDoesNotThrow(AssertDoesNotThrow.java:36)
	at org.junit.jupiter.api.Assertions.assertDoesNotThrow(Assertions.java:3199)
	at org.springframework.ai.vectorstore.pgvector.PgVectorStoreAutoTruncationIT.lambda$testAutoTruncationWithLargeDocument$3(PgVectorStoreAutoTruncationIT.java:105)
	at org.springframework.boot.test.context.runner.AbstractApplicationContextRunner.accept(AbstractApplicationContextRunner.java:469)

and

org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'org.springframework.ai.embedding.BatchingStrategy' available

	at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:394)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:385)
	at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1290)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
	at java.base/java.lang.reflect.Method.invoke(Method.java:580)
	at org.springframework.boot.test.context.assertj.AssertProviderApplicationContextInvocationHandler.invokeApplicationContextMethod(AssertProviderApplicationContextInvocationHandler.java:147)
	at org.springframework.boot.test.context.assertj.AssertProviderApplicationContextInvocationHandler.invoke(AssertProviderApplicationContextInvocationHandler.java:85)
	at jdk.proxy2/jdk.proxy2.$Proxy77.getBean(Unknown Source)
	at org.springframework.ai.vectorstore.pgvector.PgVectorStoreAutoTruncationIT.lambda$testExceedingArtificialLimit$5(PgVectorStoreAutoTruncationIT.java:142)

[sobychacko]

@markpollack Sorry about that. It is fixed now.

[markpollack]

great, merged in 8f879aa