fix: include furniture field in DoclingDocument (#387)

Author: mohammedfaisal

docling-core/src/main/java/ai/docling/core/DoclingDocument.java

@@ -44,6 +44,10 @@ public class DoclingDocument {
   @JsonProperty("body")
   private GroupItem body;
 
+  @JsonProperty("furniture")
+  @Nullable
+  private GroupItem furniture;
+
   @JsonProperty("groups")
   @JsonSetter(nulls = Nulls.AS_EMPTY)
   @lombok.Singular

docling-core/src/test/java/ai/docling/core/DoclingDocumentTests.java

@@ -4,7 +4,12 @@
 
 import org.junit.jupiter.api.Test;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import ai.docling.core.DoclingDocument.ContentLayer;
 import ai.docling.core.DoclingDocument.DocItemLabel;
+import ai.docling.core.DoclingDocument.GroupItem;
+import ai.docling.core.DoclingDocument.GroupLabel;
 import ai.docling.core.DoclingDocument.TitleItem;
 
 /**
@@ -35,4 +40,49 @@ void shouldBuildDocumentWithProperties() {
     assertThat(titleItem.getText()).isEqualTo("Docling Rocks!");
   }
 
+  @Test
+  void shouldSerializeFurnitureField() throws Exception {
+    ObjectMapper mapper = new ObjectMapper();
+    GroupItem furniture = GroupItem.builder()
+        .selfRef("#/furniture")
+        .contentLayer(ContentLayer.FURNITURE)
+        .label(GroupLabel.UNSPECIFIED)
+        .name("_root_")
+        .build();
+
+    DoclingDocument document = DoclingDocument.builder()
+        .name("test-document")
+        .furniture(furniture)
+        .build();
+
+    String json = mapper.writeValueAsString(document);
+
+    assertThat(json).contains("\"furniture\"");
+    assertThat(json).contains("\"content_layer\":\"furniture\"");
+  }
+
+  @Test
+  void shouldDeserializeFurnitureField() throws Exception {
+    ObjectMapper mapper = new ObjectMapper();
+    String json = """
+        {
+          "name": "test-document",
+          "furniture": {
+            "self_ref": "#/furniture",
+            "children": [],
+            "content_layer": "furniture",
+            "name": "_root_",
+            "label": "unspecified"
+          }
+        }
+        """;
+
+    DoclingDocument document = mapper.readValue(json, DoclingDocument.class);
+
+    assertThat(document.getFurniture()).isNotNull();
+    assertThat(document.getFurniture().getSelfRef()).isEqualTo("#/furniture");
+    assertThat(document.getFurniture().getContentLayer()).isEqualTo(ContentLayer.FURNITURE);
+    assertThat(document.getFurniture().getLabel()).isEqualTo(GroupLabel.UNSPECIFIED);
+  }
+
 }