Add auto-configuration for Observations in Spring-WS

[johkin]

I have added support for Observations in Spring-WS, and the next step would be to add auto-configuration for the ObservationInterceptors.

As far as I can tell, it could perhaps be implemented in the module spring-boot-actuator-autoconfigure under the package
org.springframework.boot.actuate.autoconfigure.observation.webservice.client or org.springframework.boot.actuate.autoconfigure.observation.webservice.server

For the WebServiceTemplate, the interceptor could probably be added by implementing a WebServiceTemplateCustomizer that is added to the context.
Condition for activating the configuration class could perhaps be @ConditionalOnBean(ObservationRegistry.class)

For the server Endpoints, the interceptor could probably be added in the addInterceptors-callback in the WsConfigurerAdapter.
Condition for activating the configuration class could perhaps be @ConditionalOnBean(ObservationRegistry.class)

The new Observation was merged in spring-projects/spring-ws#1438 for the issue
spring-projects/spring-ws#1094

This is also related to #15390

[bclozel]

What's the timeline for this feature? I'm not sure how we can properly schedule this on our side.

spring-projects/spring-ws#1438 has been merged but there is no milestone assigned; spring-projects/spring-ws#1094 is not resolved so I guess this means that the observability feature is not complete? It looks like it's merged in the main branch along with 15+ other commits and built as 4.1.0-SNAPSHOT, but the 4.1.0 milestone is in a strange state with a declined issue scheduled in it and zero closed issue (so no way for us to understand what's currently shipped as 4.1.0-SNAPSHOT.

@corneil can you clarify the situation please.