admin: Display email addresses in user-edit widget.

When the user logs in as an admin, and clicks on the 'edit user'
button under the url path #organization/user-list-admin, the modal
that was displayed didn't contain the user's email address under the
list of information. This commit adds the email input as a readonly
element, which at the very least provides helpful confirmation that
you have the right user.

Fixes part of #11453.

static/js/settings_users.js

@@ -337,6 +337,7 @@ exports.on_load_success = function (realm_people_data) {
     function open_user_info_form_modal(person) {
         var html = templates.render('user-info-form-modal', {
             user_id: person.user_id,
+            email: person.email,
             full_name: people.get_full_name(person.user_id),
             is_admin: person.is_admin,
             is_guest: person.is_guest,

static/templates/user-info-form-modal.handlebars

@@ -15,6 +15,10 @@
                     <label for="full_name">{{t "Full name" }}</label>
                     <input type="text" autocomplete="off" name="full_name" value="{{ full_name }}" />
                 </div>
+                <div class="input-group email_change_container">
+                    <label for="email">{{t "Email" }}</label>
+                    <input type="text" autocomplete="off" name="email" value="{{ email }}" readonly/>
+                </div>
                 {{#if is_bot}}
                 <div class="input-group edit_bot_owner_container">
                     <label for="bot_owner_select">{{t "Owner" }}</label>