UX: show user email when unsubscribing

app/views/email/unsubscribe.html.erb

@@ -13,6 +13,7 @@
   <%- else %>
     <br/>
     <h2><%= t 'unsubscribe.title'%></h2>
+    <div><%= t('unsubscribe.email_description', email: @user.email).html_safe %></div>
     <br/>
     <%= form_tag(email_perform_unsubscribe_path(key: params[:key])) do %>
       <%if @topic %>

config/locales/server.en.yml

@@ -728,6 +728,7 @@ en:
 
   unsubscribe:
     title: "Unsubscribe"
+    email_description: "You are unsubscribing emails for <b>%{email}</b>."
     stop_watching_topic: "Stop watching this topic, %{link}"
     mute_topic: "Mute all notifications for this topic, %{link}"
     unwatch_category: "Stop watching all topics in %{category}"