Use dependency injection when possible

I am working on this.

Actually, this issue is about dependency injection, not coding standards.

+   /**
+   * Config Factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory
+   */
+  protected $configFactory;
+
+  /**
+   * Messenger.
+   *
+   * @var \Drupal\Core\Messenger\Messenger
+   */
+  protected $messenger;
+
+  /**
+   * Logger.
+   *
+   * @var \Drupal\Core\Logger\LoggerChannelFactoryInterface
+   */
+  protected $loggerFactory;

The descriptions are each missing a definite article.

+   * Class Constructor.
+   * @param \Drupal\Core\Config\ConfigFactory $configFactory
+   *   Config Factory.
+   * @param \Drupal\Core\Messenger\Messenger $messenger
+   *   Messenger. 
+   * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $loggerFactory
+   *   Logger.
+   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
+   *   The request stack.

The description for a constructor must start with Constructs a new followed by the class name (including its namespace), and end with object.
There must be an empty line between the short description and the list of parameters.

+  public function __construct(
+    ConfigFactory $configFactory,  
+    Messenger $messenger,
+    LoggerChannelFactoryInterface $loggerFactory,
+    RequestStack $request_stack
+    ) {
+    $this->configFactory = $configFactory;
+    $this->messenger = $messenger;
+    $this->loggerFactory = $loggerFactory;
+    $this->requestStack = $request_stack;
+  }

Method declarations are written on a single line.

+  public static function create(ContainerInterface $container) {
+        return new static(
+          $container->get('config.factory'),
+          $container->get('messenger'),
+          $container->get('logger.factory'),
+          $container->get('request_stack')
+        );
+      }

As per Drupal coding standards, indentation is two spaces.

@apaderno,

Pushed the latest changes as per your comment, Also I have run phpcbf commands to fix some automatic changes. Please review.

+  /**
+   * The config factory service.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory
+   */
+  protected $configFactory;
+
+  /**
+   * The messenger service.
+   *
+   * @var \Drupal\Core\Messenger\Messenger
+   */
+  protected $messenger;

In both the cases, there is no need to say it is a service.

+  /**
+   * A logger instance.
+   *
+   * @var \Drupal\Core\Logger\LoggerChannelFactoryInterface
+   */
+  protected $loggerFactory;
+

It is sufficient to say The logger.

+  /**
+   * Constructs a new AutoWebhook object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactory $configFactory
+   *   Config Factory.
+   * @param \Drupal\Core\Messenger\Messenger $messenger
+   *   Messenger.
+   * @param \Drupal\Core\Logger\LoggerChannelFactoryInterface $loggerFactory
+   *   Logger.

The class name is missing the namespace.
The parameter descriptions are each missing a definite article.

+  protected $supportedWebhookEvents = [
+        'payment.authorized' => TRUE,
+        'payment.failed'     => TRUE,
+        'refund.created'     => TRUE
     ];

The indentation is not correct. Anyway, since this issue is for using dependency injection where possible, that change is off-topic.

+  protected function generateWebhookSecret() {
+    $alphanumericString = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ-=~!@#$%^&*()_+,./<>?;:[]{}|abcdefghijklmnopqrstuvwxyz';
 
-        return substr(str_shuffle($alphanumericString), 0, 20);
-    }
+    return substr(str_shuffle($alphanumericString), 0, 20);
+  }

This change is not replacing calls to \Drupal methods, and it is off-topic.

+  /**
+   * Constructs a new RazorpayCheckout object.

The class namespace is missing.

+    $form['display_label']['#prefix'] = 'First <a href="https://easy.razorpay.com/onboarding?recommended_product=payment_gateway&source=drupal" target="_blank">signup</a> for a Razorpay account or
+            <a href="https://dashboard.razorpay.com/signin?screen=sign_in&source=drupal" target="_blank">login</a> if you have an existing account.</p>';

Strings shown in the user interface must be translatable.

+  /**
+   * {@inheritdoc}
+   */
+  public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {
+    parent::validateConfigurationForm($form, $form_state);
+
+    if ($form_state->getErrors()) {
+      return;

+  public function onReturn(OrderInterface $order, Request $request) {
+    $keyId = $this->configuration['key_id'];
+    $keySecret = $this->configuration['key_secret'];
+    $api = new Api($keyId, $keySecret);
+
+    // Validate Rzp signature.
+    try {
+      $attributes = [
+            'razorpay_order_id' => $request->get('razorpay_order_id'),
+            'razorpay_payment_id' => $request->get('razorpay_payment_id'),
+            'razorpay_signature' => $request->get('razorpay_signature')

None of those lines have been changed to avoid calls to \Drupal methods.

+    if (substr($values['key_id'], 0, 8) !== 'rzp_' . $values['mode']) {
+      $this->messenger()->addError($this->t('Invalid Key ID or Key Secret for ' . $values['mode'] . ' mode.'));
+      $form_state->setError($form['mode']);

Translatable strings must use placeholders.

Please review.

Also, the MR changes three files, but the issue summary says four files should be changed.

Hi @apaderno,

I have fixed all the dependency injection related issues raised by you.
Please review.

Thanks