Auto-configuration of ObservationRestTemplateCustomizer fails when micrometer-core is not on the classpath

[wilkinsona]

Without micrometer-core, there's no MetricsProperties bean which causes an injection failure:

Error creating bean with name 'observationRestTemplateCustomizer' defined in class path resource [org/springframework/boot/actuate/autoconfigure/metrics/web/client/RestTemplateObservationConfiguration.class]: Unsatisfied dependency expressed through method 'observationRestTemplateCustomizer' parameter 2: No qualifying bean of type 'org.springframework.boot.actuate.autoconfigure.metrics.MetricsProperties' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}

Until we've dropped the usage of MetricsProperties and switched over entirely to ObservationProperties, we need to make sure MetricsProperties has been enabled.

[wilkinsona]

With thanks to @ryanjbaxter for pointing out the problem, we need to take a different approach here as MetricsProperties is tightly coupled to Micrometer Metrics. It references AutoTimeProperties which depends on io.micrometer.core.instrument.Timer.Builder.