Add "Remember me" checkbox to LDAP signin form.

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 7.12.0 (unreleased)
+  - Add "Remember me" checkbox to LDAP signin form.
   - Don't notify users mentioned in code blocks or blockquotes.
   - Omit link to generate labels if user does not have access to create them (Stan Hu)
   - Disable changing of the source branch in merge request update API (Stan Hu)

app/controllers/omniauth_callbacks_controller.rb

@@ -24,7 +24,7 @@ class OmniauthCallbacksController < Devise::OmniauthCallbacksController
     @user = Gitlab::LDAP::User.new(oauth)
     @user.save if @user.changed? # will also save new users
     gl_user = @user.gl_user
-    gl_user.remember_me = true if @user.persisted?
+    gl_user.remember_me = params[:remember_me] if @user.persisted?
 
     # Do additional LDAP checks for the user filter and EE features
     if @user.allowed?

app/views/devise/sessions/_new_ldap.html.haml

 = form_tag(user_omniauth_callback_path(server['provider_name']), id: 'new_ldap_user' ) do
   = text_field_tag :username, nil, {class: "form-control top", placeholder: "#{server['label']} Login", autofocus: "autofocus"}
   = password_field_tag :password, nil, {class: "form-control bottom", placeholder: "Password"}
+  - if devise_mapping.rememberable?
+    .remember-me.checkbox
+      %label{for: "remember_me"}
+        = check_box_tag :remember_me, '1', false, id: 'remember_me'
+        %span Remember me
   = button_tag "#{server['label']} Sign in", class: "btn-save btn"