Add PBS Account registration flow route

social_auth_pbs.routing.yml

@@ -8,6 +8,16 @@ social_auth_pbs.redirect_to_pbs:
   options:
     no_cache: TRUE
 
+social_auth_pbs.redirect_to_pbs_register:
+  path: 'user/login/pbs-register'
+  defaults:
+    _controller: '\Drupal\social_auth_pbs\Controller\PbsRegisterController::redirectToProvider'
+  requirements:
+    # Anonymous users can log in, but authenticated users can also associate a new provider.
+    _access: 'TRUE'
+  options:
+    no_cache: TRUE
+
 social_auth_pbs.redirect_to_apple:
   path: 'user/login/pbs-apple'
   defaults:

src/Controller/PbsRegisterController.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\social_auth_pbs\Controller;
+
+use Drupal\Core\Routing\TrustedRedirectResponse;
+
+/**
+ * Returns responses for special Social Auth PBS Account register routes.
+ *
+ * This controller generates a URL that sends the user first through an account
+ * creation flow and then through the regular OAuth2 authorization flow.
+ */
+class PbsRegisterController extends PbsAuthController {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function redirectToProvider() {
+    $response = parent::redirectToProvider();
+    if ($response instanceof TrustedRedirectResponse) {
+      $url_parts = parse_url($response->getTargetUrl());
+      $next = urlencode("{$url_parts['path']}?{$url_parts['query']}");
+      $register_url = "{$url_parts['scheme']}://{$url_parts['host']}/oauth2/register/?next=$next";
+      $response->setTrustedTargetUrl($register_url);
+    }
+    return $response;
+  }
+
+}