Fix the issues reported by phpcs

Fixed all the issues reported by PHPCS.
kindly review.

-  public function __construct(StreamWrapperManagerInterface $streamWrapperManager, LinkCrypter $link_crypter) {
+  public function __construct(StreamWrapperManagerInterface $streamWrapperManager, LinkCrypter $linkCrypter) {

It is not necessary to change the parameter name, since $link_crypter is still correct, as local variable name. Drupal coding standards say that class properties should not use snake case names, but local variables are still allowed to use that name style.

+  /**
+   * Constructs for CryptSettingsForm.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config_factory service.
+   * @param \Drupal\Core\File\FileSystemInterface $fileSystem
+   *   The fileSystem service.
+   * @param \Drupal\encrypted_link_formatter\LinkCrypter $linkCrypter
+   *   LinkCrypter service.
+   * @param \Drupal\Core\Cache\CacheTagsInvalidatorInterface $cacheTagsInvalidator
+   *   The cacheTagsInvalidator service.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory, FileSystemInterface $fileSystem, LinkCrypter $linkCrypter, CacheTagsInvalidatorInterface $cacheTagsInvalidator) {

Grammatically, construct needs a direct object; constructs for is wrong.
The class name does not have its namespace.

+  /**
+   * A helping function which generates invalidate tags.
+   */
+  protected function generateIv($type): bool {
+    $private_dir = $this->fileSystem->realpath('private://');
+    if (!$this->linkCrypter->ensureDirExists("$private_dir/iv")) {
       return FALSE;
     }

The short description should start with a verb.

+  /**
+   * A helper function for checking field defination.
+   */
   public static function isApplicable(FieldDefinitionInterface $field_definition) {
     $uri_scheme = $field_definition->getItemDefinition()->getSetting('uri_scheme');
     if ($uri_scheme === 'private') {
       return TRUE;
     }
-
     return FALSE;
   }

defination is a typo.
The short description does not make clear what the method does.
The parameter description is missing, as well as the return value description.

Intradiff file for phpcs issues and suggestions on comment #4.

-   *   The stream wrapper manager.
+   *   The streamWrapper manager.
+   * @param \Drupal\encrypted_link_formatter\LinkCrypter $link_crypter
+   *   The linkCrypter service.

Both the descriptions are wrong, since they merge into a word what are two words.

-      $this->moduleHandler()->invokeAll('alter_file_uri', [&$uri, $queryParams, &$headers, $scheme]);
+      $this->moduleHandler()->invokeAll('alter_file_uri', [&$uri, $queryParams,
+        &$headers, $scheme,
+      ]
+        );

The last two lines are wrongly indented.

+  /**
+   * The Crypt settings form constructor.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config_factory service.
+   * @param \Drupal\Core\File\FileSystemInterface $fileSystem
+   *   The fileSystem service.
+   * @param \Drupal\encrypted_link_formatter\LinkCrypter $linkCrypter
+   *   LinkCrypter service.
+   * @param \Drupal\Core\Cache\CacheTagsInvalidatorInterface $cacheTagsInvalidator
+   *   The cacheTagsInvalidator service.

The description for a method starts with a verb.

+  public function __construct(ConfigFactoryInterface $config_factory, FileSystemInterface $fileSystem, LinkCrypter $linkCrypter, CacheTagsInvalidatorInterface $cacheTagsInvalidator) {
     parent::__construct($config_factory);
-    $this->file_system = $file_system;
-    $this->link_crypter = $link_crypter;
-    $this->cache_tags_invalidator = $cache_tags_invalidator;
+    $this->fileSystem = $fileSystem;
+    $this->linkCrypter = $linkCrypter;
+    $this->cacheTagsInvalidator = $cacheTagsInvalidator;

There is no need to change the scheme used for the local variables. Snake case is allowed for them.

+  /**
+   * Helping function which generates invalidate tags.
+   */

It should be helper function, but Helping function which is not necessary. A method description starts with a verb.
The description of parameters and return value is still missing.

   /**
    * Constructs an Example object.
    *
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
    *   The config factory.
+   * @param \Drupal\Core\File\FileSystemInterface $fileSystem
+   *   The fileSystem service.
    */

Since that comment is changed, the class name should also include its namespace.

+  /**
+   * A helper function to ensure Directory Exists.
+   */

Directory and Exists are not at the beginning of a sentence. In English, those words are not written in capital case.
The description is still wrong.

+   * @param \Drupal\Core\Routing\RouteMatchInterface $routeMatch
+   *   RouteMatch service.
+   * @param \Drupal\encrypted_link_formatter\LinkCrypter $link_crypter
+   *   LinkCrypter service.
    */

There are missing articles and words merged in a single word.

Changing to unassigned since there is no update for a while

Automatically closed - issue fixed for 2 weeks with no activity.