Add deprecation warning to calendar index page

[ci skip]

app/views/work_packages/calendars/index.html.erb

@@ -27,6 +27,14 @@ See doc/COPYRIGHT.rdoc for more details.
 
 ++#%>
 <%= toolbar title: (@query.new_record? ? l(:label_calendar) : @query.name) %>
+
+<div class="notification-box -warning">
+  <a title="close" class="notification-box--close icon-context icon-close"></a>
+  <div class="notification-box--content">
+    <p><%= t('deprecations.calendar.removal')%></p>
+  </div>
+</div>
+
 <%= form_tag(work_packages_calendar_index_path, method: :get, id: 'query_form') do %>
   <%= hidden_field_tag('project_id', @project.to_param) if @project %>
   <%= hidden_field_tag('set_filter', 1) %>

config/locales/en.yml

@@ -96,6 +96,8 @@ en:
       further_information_before: "Please take a look at"
       link_name: "how to migrate to the new timeline."
       further_information_after: ""
+    calendar:
+      removal: "Please note: This module is going to be removed with OpenProject 8.0."
 
   groups:
     index: