fix: not able to create recurring deposit product (#1712)

now we are able to create recurring deposit product by adding one slab and using information
from JIRA how to fill it

Fixes: #1705

src/app/products/recurring-deposit-products/recurring-deposit-product-stepper/recurring-deposit-product-interest-rate-chart-step/recurring-deposit-product-interest-rate-chart-step.component.html

@@ -60,6 +60,10 @@
           </button>
         </div>
 
+        <div fxFlex="100%" *ngIf="chart.value.chartSlabs.length === 0">
+          <h3 class="mat-h3">It's required to add at least one Slab</h3>  
+        </div>
+
         <table fxFlex="98%" class="mat-elevation-z1" mat-table [dataSource]="chart.value.chartSlabs" *ngIf="chart.value.chartSlabs.length !== 0" multiTemplateDataRows>
 
           <ng-container matColumnDef="period">

src/app/products/recurring-deposit-products/recurring-deposit-product-stepper/recurring-deposit-product-interest-rate-chart-step/recurring-deposit-product-interest-rate-chart-step.component.ts

@@ -229,7 +229,7 @@ export class RecurringDepositProductInterestRateChartStepComponent implements On
       'fromDate': ['', Validators.required],
       'endDate': [''],
       'isPrimaryGroupingByAmount': [false],
-      'chartSlabs': this.formBuilder.array([])
+      'chartSlabs': this.formBuilder.array([], Validators.required)
     });
   }