Fix System-wide Alert accessibility issues

- Added missing aria-label to buttons

Author: alexandrevryghem

src/app/system-wide-alert/alert-form/system-wide-alert-form.component.html

@@ -30,6 +30,7 @@ <h2 id="header">{{'system-wide-alert.form.header' | translate}}</h2>
     <div class="row">
         <div class="col mb-2 d-flex align-items-end">
             <ui-switch size="small"
+                       [ariaLabel]="'system-wide-alert.form.label.countdownTo.enable' | translate"
                        [checked]="counterEnabled$ |async"
                        (change)="setCounterEnabled($event)"></ui-switch>
             <span class="ml-2">{{ 'system-wide-alert.form.label.countdownTo.enable' | translate }}</span>
@@ -49,8 +50,9 @@ <h2 id="header">{{'system-wide-alert.form.header' | translate}}</h2>
                             #d="ngbDatepicker"
                             (ngModelChange)="updatePreviewTime()"
                     />
-                    <button class="btn btn-outline-secondary fas fa-calendar" (click)="d.toggle()"
-                            type="button"></button>
+                    <button [attr.aria-label]="'system-wide-alert-form.select-date-by-calendar' | translate"
+                            (click)="d.toggle()" class="btn btn-outline-secondary fas fa-calendar" type="button">
+                    </button>
                 </div>
             </div>
             <div class="col-12 d-md-none">

src/assets/i18n/en.json5

@@ -5168,6 +5168,8 @@
 
   "system-wide-alert.form.label.countdownTo.hint": "Hint: Set a countdown timer. When enabled, a date can be set in the future and the system-wide alert banner will perform a countdown to the set date. When this timer ends, it will disappear from the alert. The server will NOT be automatically stopped.",
 
+  "system-wide-alert-form.select-date-by-calendar": "Select date using calendar",
+
   "system-wide-alert.form.label.preview": "System-wide alert preview",
 
   "system-wide-alert.form.update.success": "The system-wide alert was successfully updated",