feat: Enhancing debug information for HttpDataSource transfers

spi/data-plane/data-plane-spi/src/main/java/org/eclipse/edc/connector/dataplane/spi/pipeline/StreamFailure.java

@@ -29,6 +29,12 @@ public StreamFailure(List<String> messages, Reason reason) {
         this.reason = reason;
     }
 
+    @Override
+    public String getFailureDetail() {
+        var str = super.getFailureDetail();
+        return (str != null && !str.isEmpty()) ? (reason + ": " + str) : (reason + "");
+    }
+
     public Reason getReason() {
         return reason;
     }

spi/data-plane/data-plane-spi/src/test/java/org/eclipse/edc/connector/dataplane/spi/pipeline/StreamFailureTest.java

@@ -0,0 +1,43 @@
+/*
+ *  Copyright (c) 2024 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ *
+ *  This program and the accompanying materials are made available under the
+ *  terms of the Apache License, Version 2.0 which is available at
+ *  https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Contributors:
+ *       Bayerische Motoren Werke Aktiengesellschaft (BMW AG) - Initial implementation
+ *
+ */
+
+package org.eclipse.edc.connector.dataplane.spi.pipeline;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.eclipse.edc.connector.dataplane.spi.pipeline.StreamFailure.Reason.NOT_FOUND;
+
+public class StreamFailureTest {
+    private static final String failureMessage = "failure message";
+
+    @Test
+    void verify_with_failureDetail_message_starts_with_reason() {
+        assertThat(new StreamFailure(List.of(failureMessage), NOT_FOUND)
+                .getFailureDetail()
+                .startsWith(NOT_FOUND.toString())
+        ).isTrue();
+    }
+
+    @Test
+    void verify_with_failureDetail_message_only_contains_reason_when_message_is_empty() {
+        assertThat(new StreamFailure(Collections.emptyList(), NOT_FOUND)
+                .getFailureDetail()
+                .equals(NOT_FOUND.toString())
+        ).isTrue();
+    }
+}