Give Admin email an interface

app/controllers/admin/emails_controller.rb

 class Admin::EmailsController < Admin::ApplicationController
   def show
-    render text: 'hello world'
   end
 end

app/helpers/admin_email_helper.rb

+module AdminEmailHelper
+  def admin_email_grouped_recipient_options
+    options_for_select([['Everyone', 'all']]) +
+    grouped_options_for_select(
+      'Groups' => Group.pluck(:name, :id).map{ |name, id| [name, "group_#{id}"] },
+      'Projects' => grouped_project_list
+    )
+  end
+
+  protected
+  def grouped_project_list
+    Group.includes(:projects).flat_map do |group|
+      group.human_name
+      group.projects.map do |project|
+        ["#{group.human_name} / #{project.name}", "project_#{project.id}"]
+      end
+    end
+  end
+end
\ No newline at end of file

app/views/admin/emails/show.html.haml

+%h3.page-title
+  Send email notication
+%p.light
+  You can notify the app / group or a project by sending them an email notification
+
+= form_tag admin_email_path, class: 'form-horizontal' do
+  .form-group
+    %label.control-label{for: :subject} Subject
+    .col-sm-10
+      = text_field_tag :subject, '', class: 'form-control'
+
+  .form-group
+    %label.control-label{for: :body} Body
+    .col-sm-10
+      = text_area_tag :body, '', class: 'form-control', rows: 15
+
+  .form-group
+    %label.control-label{for: :recipients} Recipients
+    .col-sm-10
+      = select_tag :recipients,  admin_email_grouped_recipient_options, class: :select2
+
+  .form-actions
+    = submit_tag 'Send message', class: 'btn btn-create'