consumer_permissions.module

<?php

/**
 * @file
 * Provides user permissions to authenticate with certain consumers.
 */

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Url;

/**
 * Implements hook_form_ENTITY_TYPE_form_alter() for consumer form.
 */
function consumer_permissions_form_consumer_form_alter(array &$form, FormStateInterface $form_state): void {
  array_unshift($form['actions']['submit']['#submit'],
    'consumer_permissions_consumer_form_submit_message');
}

/**
 * Adds message to notify about client permissions.
 */
function consumer_permissions_consumer_form_submit_message(array &$form, FormStateInterface $form_state): void {
  $url = Url::fromRoute('user.admin_permissions.module', ['modules' => 'consumer_permissions']);
  if ($url->access(\Drupal::currentUser())) {
    /** @var \Drupal\Core\Entity\EntityFormInterface $form_object */
    $form_object = $form_state->getFormObject();
    $client = $form_object->getEntity();
    if ($client->isNew()) {
      \Drupal::messenger()->addMessage(
        t('Configure <a href=":link">related permissions</a> for consumer %client.', [
          ':link' => $url->toString(),
          '%client' => $form_state->getValue('label')[0]['value'],
        ])
      );
    }
  }
}