TagPropagationFinishedSpanHandler not auto-configured with yml

[dlsrb6342]

Bug report

SleuthTagPropagationAutoConfiguration cannot auto-configured with yaml.
TagPropagationFinishedSpanHandler Bean is conditional on spring.sleuth.propagation.tag.whitelisted-keys

spring-cloud-sleuth/spring-cloud-sleuth-core/src/main/java/org/springframework/cloud/sleuth/propagation/SleuthTagPropagationAutoConfiguration.java

Lines 44 to 50 in 59216c3

	@Bean
	@ConditionalOnProperty("spring.sleuth.propagation.tag.whitelisted-keys")
	public FinishedSpanHandler finishedSpanHandler(SleuthProperties sleuthProperties,
	SleuthTagPropagationProperties tagPropagationProperties) {
	return new TagPropagationFinishedSpanHandler(sleuthProperties,
	tagPropagationProperties);
	}

If you use properties file not yml, it works well. In TagPropagationFinishedSpanHandlerTest.java, it use properties. So it could be passed I think.

spring-cloud-sleuth/spring-cloud-sleuth-core/src/test/java/org/springframework/cloud/sleuth/propagation/TagPropagationFinishedSpanHandlerTest.java

Lines 45 to 50 in 59216c3

	@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE, properties = {
	"spring.sleuth.baggage-keys=my-baggage",
	"spring.sleuth.propagation-keys=my-propagation,others-propagation",
	"spring.sleuth.propagation.tag.whitelisted-keys=my-baggage,my-propagation" },
	classes = TagPropagationFinishedSpanHandlerTest.TestConfiguration.class)
	public class TagPropagationFinishedSpanHandlerTest {

But if you use yml file, Condition cannot be matched with yml list syntax.

spring.sleuth.propagation.tag.whitelisted-keys: [foo, bar]

spring.sleuth.propagation.tag.whitelisted-keys: 
  - foo
  - bar

All above two cases doesn't work.

ConditionalOnProperty annotation cannot be used with Collections. Please check below javadoc link.
https://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/autoconfigure/condition/ConditionalOnProperty.html

I think it have to apply custom Conditional annotation for colleciton. Or just make bean when spring.sleuth.propagation.tag.enabled is true.

FYI, If you want to use TagPropagationFinishedSpanHandler with yml file, Only spring.sleuth.propagation.tag.whitelisted-keys: foo,bar works.