Add document upload from admin section

app/controllers/admin/site_customization/documents_controller.rb

@@ -0,0 +1,40 @@
+class Admin::SiteCustomization::DocumentsController < Admin::SiteCustomization::BaseController
+
+  def index
+    @documents = Document.admin.page(params[:page])
+  end
+
+  def new
+    @document = Document.new
+  end
+
+  def create
+    @document = initialize_document
+    if @document.save
+      notice = t("admin.documents.create.success_notice")
+      redirect_to admin_site_customization_documents_path, notice: notice
+    else
+      notice = t("admin.documents.create.unable_notice")
+      redirect_to new_admin_site_customization_document_path, notice: notice
+    end
+  end
+
+  def destroy
+    @document = Document.find(params[:id])
+    @document.destroy
+
+    notice = t("admin.documents.destroy.success_notice")
+    redirect_to admin_site_customization_documents_path, notice: notice
+  end
+
+  private
+
+    def initialize_document
+      document = Document.new
+      document.attachment = params.dig(:document, :attachment)
+      document.title = document.attachment_file_name
+      document.user = current_user
+      document.admin = true
+      document
+    end
+end