If there's a ?next param, redirect there instead of dashboard after login

lms/templates/login_modal.html

@@ -46,7 +46,11 @@
 (function() {
    $(document).delegate('#login_form', 'ajax:success', function(data, json, xhr) {
      if(json.success) {
-       location.href="${reverse('dashboard')}";
+       % if request.REQUEST.get('next', False):
+           location.href="${request.REQUEST.get('next')}";
+       % else:
+           location.href="${reverse('dashboard')}";
+       % endif
      } else {
        if($('#login_error').length == 0) {
          $('#login_form').prepend('<div id="login_error" class="modal-form-error"></div>');