chore: handle forbidden username exceptions on registration

Port of master commit 58ec90ac.

Co-Authored-By: Adolfo R. Brandes <adolfo@axim.org>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/register/components/RegistrationFailure.jsx

@@ -8,6 +8,7 @@ import PropTypes from 'prop-types';
 import { windowScrollTo } from '../../data/utils';
 import {
   FORBIDDEN_REQUEST,
+  FORBIDDEN_USERNAME,
   INTERNAL_SERVER_ERROR,
   TPA_AUTHENTICATION_FAILURE,
   TPA_SESSION_EXPIRED,
@@ -49,6 +50,9 @@ const RegistrationFailureMessage = (props) => {
     case TPA_SESSION_EXPIRED:
       errorMessage = formatMessage(messages['registration.tpa.session.expired'], { provider: context.provider });
       break;
+    case FORBIDDEN_USERNAME:
+      errorMessage = formatMessage(messages['registration.forbidden.username']);
+      break;
     default:
       errorMessage = formatMessage(messages['registration.empty.form.submission.error']);
       break;

src/register/data/constants.js

@@ -11,3 +11,4 @@ export const FORM_SUBMISSION_ERROR = 'form-submission-error';
 export const INTERNAL_SERVER_ERROR = 'internal-server-error';
 export const TPA_AUTHENTICATION_FAILURE = 'tpa-authentication-failure';
 export const TPA_SESSION_EXPIRED = 'tpa-session-expired';
+export const FORBIDDEN_USERNAME = 'forbidden-username';

src/register/messages.jsx

@@ -162,6 +162,11 @@ const messages = defineMessages({
     defaultMessage: 'Registration using {provider} has timed out.',
     description: 'Error message that appears when a user has not registered in the required timeframe for the registration method they chose.',
   },
+  'registration.forbidden.username': {
+    id: 'registration.forbidden.username',
+    defaultMessage: 'Usernames can\'t include words that could be mistaken for course roles. Please choose a different username.',
+    description: 'Error message when a user tries to register with a username that contains forbidden words',
+  },
   'registration.tpa.authentication.failure': {
     id: 'registration.tpa.authentication.failure',
     defaultMessage: 'We are sorry, you are not authorized to access {platform_name} via this channel. '