Add setting "disable_delete_all_announcements"

See BT#13077

main/announcements/announcements.php

@@ -314,8 +314,12 @@ switch ($action) {
         break;
     case 'delete_all':
         if (api_is_allowed_to_edit()) {
+            $allow = api_get_configuration_value('disable_delete_all_announcements');
+            if ($allow === false) {
                 AnnouncementManager::delete_all_announcements($_course);
                 Display::addFlash(Display::return_message(get_lang('AnnouncementDeletedAll')));
+
+            }
             header('Location: ' . $homeUrl);
             exit;
         }
@@ -668,9 +672,12 @@ if ($allowToEdit && (empty($_GET['origin']) || $_GET['origin'] !== 'learnpath')
     }
 }
 
-if ($allowToEdit) {
+if ($allowToEdit && api_get_group_id() == 0) {
-    if (api_get_group_id() == 0) {
+    $allow = api_get_configuration_value('disable_delete_all_announcements');
-        if (!isset($_GET['action'])) {
+    if ($allow === false) {
+        if (!isset($_GET['action']) ||
+            isset($_GET['action']) && $_GET['action'] == 'list'
+        ) {
             $actionsLeft .= "<a href=\"" . api_get_self() . "?" . api_get_cidreq() . "&action=delete_all\" onclick=\"javascript:if(!confirm('" . get_lang("ConfirmYourChoice") . "')) return false;\">" .
                 Display::return_icon(
                     'delete_announce.png',

main/install/configuration.dist.php

@@ -618,6 +618,9 @@ $_configuration['gradebook_badge_sidebar'] = [
 // Hide base course announcements when entering a group.
 //$_configuration['hide_base_course_announcements_in_group'] = false;
 
+// Disable delete all announcements button
+//$_configuration['disable_delete_all_announcements'] = false;
+
 // Allow or block user subcriptions to a lp/lp category
 /*$_configuration['lp_subscription_settings'] = [
     'options' => [