Verify 'Full Name' field does not allow HTML in Signup form

'Full Name' field in the signup form is allowing HTML as an input
which makes spoofing easily.To avoid it, validation is added
that will ensure 'Full Name' field does not allow HTML.

LEARNER-3385

openedx/core/djangoapps/user_api/accounts/api.py

@@ -173,11 +173,15 @@ def update_account_settings(requesting_user, update, username=None):
                 "user_message": err.message
             }
 
-    if changing_full_name and contains_html(update['name']):
-        field_errors["name"] = {
-            "developer_message": u"Error thrown from validate_full_name: '{}'".format('Full Name is in-valid'),
-            "user_message": _(u"Full Name cannot contain the following characters: < >")
-        }
+    # If the user asked to change full name, validate it
+    if changing_full_name:
+        try:
+            student_forms.validate_name(update['name'])
+        except ValidationError as err:
+            field_errors["name"] = {
+                "developer_message": u"Error thrown from validate_name: '{}'".format(err.message),
+                "user_message": err.message
+            }
 
     # If we have encountered any validation errors, return them to the user.
     if field_errors: