Simplify code to ask for send newsletter confirmation

Using the standard `confirm` parameter, we can remove all the custom
code we added to do the same thing.

Since the code is similar, we're doing the same when asking for
confirmation to send notifications.

app/assets/javascripts/application.js

@@ -110,11 +110,9 @@
 //= require sortable
 //= require table_sortable
 //= require investment_report_alert
-//= require send_newsletter_alert
 //= require managers
 //= require i18n
 //= require globalize
-//= require send_admin_notification_alert
 //= require settings
 //= require cookies
 //= require columns_selector
@@ -166,10 +164,8 @@ var initialize_modules = function() {
   App.Sortable.initialize();
   App.TableSortable.initialize();
   App.InvestmentReportAlert.initialize();
-  App.SendNewsletterAlert.initialize();
   App.Managers.initialize();
   App.Globalize.initialize();
-  App.SendAdminNotificationAlert.initialize();
   App.Settings.initialize();
   if ($("#js-columns-selector").length) {
     App.ColumnsSelector.initialize();

app/assets/javascripts/send_admin_notification_alert.js

@@ -1,10 +0,0 @@
-(function() {
-  "use strict";
-  App.SendAdminNotificationAlert = {
-    initialize: function() {
-      $("#js-send-admin_notification-alert").on("click", function() {
-        return confirm(this.dataset.alert);
-      });
-    }
-  };
-}).call(this);

app/assets/javascripts/send_newsletter_alert.js

@@ -1,10 +0,0 @@
-(function() {
-  "use strict";
-  App.SendNewsletterAlert = {
-    initialize: function() {
-      $("#js-send-newsletter-alert").on("click", function() {
-        return confirm(this.dataset.alert);
-      });
-    }
-  };
-}).call(this);

app/views/admin/admin_notifications/show.html.erb

@@ -69,11 +69,10 @@
       @admin_notification,
       text: t("admin.admin_notifications.show.send"),
       method: :post,
-      "data-alert": t(
+      confirm: t(
         "admin.admin_notifications.show.send_alert",
         n: @admin_notification.list_of_recipients_count
       ),
-      id: "js-send-admin_notification-alert",
       class: "button success expanded",
     ) %>
   </div>

app/views/admin/newsletters/show.html.erb

@@ -61,8 +61,7 @@
     @newsletter,
     text: t("admin.newsletters.show.send"),
     method: :post,
-    "data-alert": t("admin.newsletters.show.send_alert", n: recipients_count),
-    id: "js-send-newsletter-alert",
+    confirm: t("admin.newsletters.show.send_alert", n: recipients_count),
     class: "button success"
   ) %>
 <% end %>