add some basic checks when batch creating users

generic/templates/generic/trainees.html

@@ -10,6 +10,7 @@
         <a href='{% url "trainees_grade" "ST"|add:i %}'>ST{{i}}</a>{% if not forloop.last %}, {% endif %}
     {% endfor %}
     (<a href="{% url 'create_trainee' %}" title="Click to add a trainee to the platform, creating an account for them.">Add trainee</a>)
+    (<a href="{% url 'accounts_bulk_create' %}" title="Click to create multiple trainees at once.">Bulk create</a>)
 
     <h2>
         {% if grade %}