Refactor findByDatasetId method in DashboardDrawerService

- Changed return type from DashboardDrawerList to DashboardDrawer
- Added logic to handle single record return
- Updated default return to an empty DashboardDrawer instance

src/main/java/edu/harvard/dbmi/avillach/dictionary/dashboarddrawer/DashboardDrawerService.java

@@ -39,12 +39,16 @@ public DashboardDrawerList findAll() {
      * @param datasetId the ID of the dataset to fetch.
      * @return a Dashboard instance with drawer-specific columns and rows.
      */
-    public DashboardDrawerList findByDatasetId(Integer datasetId) {
+    public DashboardDrawer findByDatasetId(Integer datasetId) {
         if (dashboardLayout.equalsIgnoreCase("bdc")) {
             List<DashboardDrawer> records = repository.getDashboardDrawerRows(datasetId);
-            return new DashboardDrawerList(records);
+            // Should be atomic as the query is an aggregation on the dataset table.
+            // Probably a better way to do this.
+            if (records.size() == 1) {
+                return records.get(0);
+            }
         }
 
-        return new DashboardDrawerList(new ArrayList<>());
+        return new DashboardDrawer(-1, "", "", new ArrayList<>(), "", new ArrayList<>(), "", "");
     }
 }