Set agent name and version conditionally (#229)

* Set agent name and version conditionally

* Update resource.go

Author: gregkalapos

enrichments/internal/elastic/resource.go

@@ -72,12 +72,19 @@ func (s *resourceEnrichmentContext) Enrich(resource pcommon.Resource, cfg config
 		return true
 	})
 
+	// agent.name and version are set by classic Elastic APM Agents - if the value is present, we take it
+	// otherwise the setAgent[Name|Version] functions are called to derive the values
 	if cfg.AgentName.Enabled {
-		s.setAgentName(resource)
+		if _, exists := resource.Attributes().Get(elasticattr.AgentName); !exists {
+			s.setAgentName(resource)
+		}
 	}
 	if cfg.AgentVersion.Enabled {
-		s.setAgentVersion(resource)
+		if _, exists := resource.Attributes().Get(elasticattr.AgentVersion); !exists {
+			s.setAgentVersion(resource)
+		}
 	}
+
 	if cfg.OverrideHostName.Enabled {
 		s.overrideHostNameWithK8sNodeName(resource)
 	}