Opentelemetry service.name default should align with OpenTelemetry Semantic Convention

[lenin-jaganathan]

spring-boot/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/opentelemetry/OpenTelemetryAutoConfiguration.java

Line 54 in 4bc63b5

private static final String DEFAULT_APPLICATION_NAME = "application";

Spring's Opentelemetry auto configuration seem to use application as a fall back value when the property spring.application.name is not set. As per Opentelemetry semantic convention, the default value when the app name is not available should be unknown_service.

Note: Micrometer also defaults to the value unknown_service. But when used with spring's auto configuration the resource is set to a different value.

[mhalbritter]

Superseded by #38219.