Fix: remove gcp project and get host-project ID

gcp/logback-logstash-encoder-gcp/src/main/java/no/entur/logging/cloud/gcp/logback/logstash/StackdriverLogstashEncoder.java

@@ -63,13 +63,43 @@ protected AbstractCompositeJsonFormatter<ILoggingEvent> createFormatter() {
 		return formatter;
 	}
 
+	private static final String OTEL_GCP_PROJECT_ID_ATTRIBUTE = "gcp.project_id";
+
+	/**
+	 * Resolves the GCP project that traces are stored in, so it can be embedded in the
+	 * 'projects/{projectId}/traces/{traceId}' value written to the log entry.
+	 * 
+	 * On Kubernetes, traces are exported to the cluster's host project (ent-kub-<env>),
+	 * which differs from the workload's own project. That destination project is carried in the
+	 * 'gcp.project_id' OpenTelemetry resource attribute, so it takes precedence. Runtimes that
+	 * still export traces to their own project (e.g. Cloud Run, Firebase) fall back to
+	 * 'GOOGLE_CLOUD_PROJECT'.
+	 */
 	private static String resolveProjectId() {
-	    for (String envName : new String[]{"GOOGLE_CLOUD_PROJECT", "GCP_PROJECT_ID"}) {
-	        String projectId = System.getenv(envName);
-	        if (projectId != null && !projectId.isBlank()) {
-	            return projectId;
-	        }
-	    }
-	    return null;
+		String projectId = resolveOtelResourceAttribute(OTEL_GCP_PROJECT_ID_ATTRIBUTE);
+		if (projectId != null) {
+			return projectId;
+		}
+		String fallback = System.getenv("GOOGLE_CLOUD_PROJECT");
+		return (fallback == null || fallback.isBlank()) ? null : fallback;
 	}
+
+	private static String resolveOtelResourceAttribute(String attributeName) {
+		String otelResourceAttributes = System.getenv("OTEL_RESOURCE_ATTRIBUTES");
+		if (otelResourceAttributes == null || otelResourceAttributes.isBlank()) {
+			return null;
+		}
+		for (String pair : otelResourceAttributes.split(",")) {
+			int separatorIndex = pair.indexOf('=');
+			if (separatorIndex < 0) {
+				continue;
+			}
+			if (pair.substring(0, separatorIndex).trim().equals(attributeName)) {
+				String value = pair.substring(separatorIndex + 1).trim();
+				return value.isBlank() ? null : value;
+			}
+		}
+		return null;
+	}
+
 }