fix(AnalyticalTable): add error log for nested headers (#8300)

Closes #8293

Author: Lukas742

packages/main/src/components/AnalyticalTable/index.tsx

@@ -346,6 +346,14 @@ const AnalyticalTable = forwardRef<AnalyticalTableDomRef, AnalyticalTablePropTyp
     setGlobalFilter,
   } = tableInstanceRef.current;
 
+  useEffect(() => {
+    if (process.env.NODE_ENV === 'development' && headerGroups.length > 1) {
+      console.error(
+        '[AnalyticalTable] Nested column headers are not supported. Please flatten your column definitions.',
+      );
+    }
+  }, [headerGroups.length]);
+
   const tableState: AnalyticalTableState = tableInstanceRef.current.state;
   const { popInColumns, triggerScroll } = tableState;
   const isGrouped = !!tableState.groupBy.length;

packages/main/src/components/AnalyticalTable/types/index.ts

@@ -166,6 +166,9 @@ export interface TableInstance {
   groupedFlatRows?: RowType[];
   groupedRows?: RowType[];
   groupedRowsById?: Record<string, RowType>;
+  /**
+   * Nested column headers are not supported. This array must only contain a single header group.
+   */
   headerGroups: Record<string, any>[];
   headers: ColumnType[];
   initialRows: RowType[];