fix: only use trackByProp on row level with strict type

fix `DatatableComponent.trackByProp` which always returned undefined on group level by using key as index for group.

BREAKING CHANGE: `DatatableComponent.trackByProp` input now enforce strict type check as key of row.

Before:

// Even though name is not a valid prop on rows it is allowed to be used with `trackByProp`.

```
<ngx-datatable
 trackByProp="'name'"
 [rows]="[{id: 1}, {id: 2}]"
>
```
After:
Typescript would give compilation error as name is not know property in rows.

Author: chintankavathia

projects/ngx-datatable/src/lib/components/body/body.component.ts

@@ -278,7 +278,7 @@ export class DataTableBodyComponent<TRow extends Row = any> implements OnInit, O
   readonly groupHeader = input<DatatableGroupHeaderDirective>();
   readonly selectCheck = input<(value: TRow, index: number, array: TRow[]) => boolean>();
   readonly displayCheck = input<(row: TRow, column: TableColumnInternal, value?: any) => boolean>();
-  readonly trackByProp = input<string>();
+  readonly trackByProp = input<keyof TRow>();
   readonly rowClass = input<(row: TRow) => string | Record<string, boolean>>();
   readonly groupedRows = input<Group<TRow>[]>();
   // TODO: Find a better way to handle default expansion state with signal input
@@ -394,8 +394,8 @@ export class DataTableBodyComponent<TRow extends Row = any> implements OnInit, O
         return index;
       }
       const trackByProp = this.trackByProp();
-      if (trackByProp && row) {
-        return (row as any)[trackByProp];
+      if (trackByProp && row && this.isRow(row)) {
+        return row[trackByProp];
       } else if (row && this.isGroup(row)) {
         return row.key ?? index;
       } else {

projects/ngx-datatable/src/lib/components/datatable.component.ts

@@ -420,7 +420,7 @@ export class DatatableComponent<TRow extends Row = any>
    * Property to which you can use for custom tracking of rows.
    * Example: 'name'
    */
-  @Input() trackByProp?: string;
+  @Input() trackByProp?: keyof TRow;
 
   /**
    * Property to which you can use for determining select all