Update Bootstrap to v4.1, fix chosen.js and pagedown on multiple sites

app/helpers/pagedown_form_builder.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+class PagedownFormBuilder < ActionView::Helpers::FormBuilder
+  def pagedown(method, args)
+    # Adopt simple form builder to work with form_for
+    @attribute_name = method
+    @input_html_options = args[:input_html]
+
+    @template.capture do
+      @template.concat wmd_button_bar
+      @template.concat wmd_textarea
+      @template.concat wmd_preview if show_wmd_preview?
+    end
+  end
+
+  private
+
+  def wmd_button_bar
+    @template.content_tag :div, nil, id: "wmd-button-bar-#{base_id}"
+  end
+
+  def wmd_textarea
+    @template.text_area @object_name, @attribute_name,
+                       **@input_html_options,
+                       class: 'form-control wmd-input',
+                       id: "wmd-input-#{base_id}"
+  end
+
+  def wmd_preview
+    @template.content_tag :div, nil,
+                         class: 'wmd-preview',
+                         id: "wmd-preview-#{base_id}"
+  end
+
+  def show_wmd_preview?
+    @input_html_options[:preview].present?
+  end
+
+  def base_id
+    options[:pagedown_id_suffix] || @attribute_name
+  end
+end