Issue #2921095: Fix parameters for hook_openid_connect_post_authorize call in OpenIDConnect::completeAuthorization().
Issue #2921095: Deprecate hook_openid_connect_user_properties_to_skip_alter() in favor of hook_openid_connect_user_properties_ignore_alter().
Issue #2961752: Replace 'drupal_set_message()' with messenger service in redirect controller and accounts form.
Issue #2961251 by Mario Steinitz: Allow client plugins to provide form validation/submit handler for their settings.
Issue #2960886 by Mario Steinitz: Avoid collision with other class names within the \Drupal namespace
Issue #2953825 by shobhit_juyal, dhruveshdtripathi, mohit1604, riddhi.addweb, ankitjain28may: Missing README.txt
This reverts commit 199a5c5c.