Autoconfigurable correlationScopeDecorator doesn't use builder from Spring Context

[akrikheli]

The correlationScopeDecorator creates CorrelationScopeDecorator.Builder via new operator and fully ignores builder bean:

spring-cloud-sleuth/spring-cloud-sleuth-autoconfigure/src/main/java/org/springframework/cloud/sleuth/autoconfig/brave/BraveBaggageConfiguration.java

Line 207 in fc5f26a

CorrelationScopeDecorator.Builder builder = MDCScopeDecorator.newBuilder();

Looks like bug because there's conditional
@ConditionalOnBean(CorrelationScopeDecorator.Builder.class)
over this bean.

Thus there's no way to customize builder for correlationScopeDecorator (for example if we want to add custom SingleCorrelationField with flushing on update).

I suggest to inject the builder as method parameter in java configuration of correlationScopeDecorator bean and use it.

[marcingrzejszczak]

fixed via #2285