docs: Implement guide for custom authenticator integration

docs/customization/custom_authenticators.md

@@ -0,0 +1,119 @@
+# Custom Authenticators
+
+CodeIgniter Shield allows you to extend authentication by creating **Custom Authenticators**.  
+This is done by implementing the `CodeIgniter\Shield\Authentication\AuthenticatorInterface` contract, which ensures full compatibility with Shield’s authentication lifecycle, including `login` and `logout` events.
+
+Custom Authenticators enable project-specific authentication strategies such as:
+
+- External identity providers (OAuth, SAML, OpenID Connect)  
+- Hardware or device challenges (USB Security Key, FIDO2, TPM, device fingerprinting)  
+- Hybrid authentication mechanisms  
+
+## Why Custom Authenticators
+
+While Shield provides built-in authenticators such as **Session**, **AccessTokens**, **HmacSha256**, and **JWT**, custom authenticators allow you to:
+
+- Enforce project-specific login logic  
+- Integrate new or external authentication mechanisms  
+- Keep full compatibility with Shield events and lifecycle  
+
+## Implementing a Custom Authenticator
+
+1. Create a PHP class in your `App\Auth\Authentication` namespace.
+2. Implement the `CodeIgniter\Shield\Authentication\AuthenticatorInterface`.
+3. Implement the required methods:
+
+```php
+<?php
+
+declare(strict_types=1);
+
+namespace App\Auth\Authentication;
+
+use CodeIgniter\Shield\Authentication\AuthenticatorInterface;
+use CodeIgniter\Shield\Result;
+use CodeIgniter\Shield\Entities\User;
+
+class MyCustomAuthenticator implements AuthenticatorInterface
+{
+    public function attempt(array $credentials): Result
+    {
+        // Your login logic
+    }
+
+    public function check(array $credentials): Result
+    {
+        // Credential verification
+    }
+
+    public function loggedIn(): bool
+    {
+        // Return login state
+    }
+
+    public function login(User $user): void
+    {
+        // Store user session or token
+    }
+
+    public function loginById($userId): void
+    {
+        // Optional: login using user ID
+    }
+
+    public function logout(): void
+    {
+        // Remove session or token
+    }
+
+    public function getUser(): ?User
+    {
+        // Return the currently logged-in user
+    }
+
+    public function recordActiveDate(): void
+    {
+        // Optional: track user activity
+    }
+}
+```
+
+## Registering the Authenticator
+
+In CodeIgniter Shield, all authenticators-built-in or custom—are registered through the **app/Config/Auth.php** file. This ensures that Shield recognizes your authenticator and allows you to reference it using its alias in the *auth* helper.
+
+Open **app/Config/Auth.php** and add your custom authenticator to the `$authenticators` array:
+
+```php
+public array $authenticators = [
+    'session' => \CodeIgniter\Shield\Authentication\Session::class,
+    'tokens'  => \CodeIgniter\Shield\Authentication\AccessTokens::class,
+    'hmac'    => \CodeIgniter\Shield\Authentication\HmacSha256::class,
+    //  Register your custom authenticator
+    'custom'  => \App\Auth\Authentication\MyCustomAuthenticator::class,
+];
+```
+The array key `custom` is the alias you will use in the `auth('custom')` helper.
+
+## Using the Authenticator
+
+You can now use your authenticator anywhere in your application via the `auth('custom')` helper:
+
+```php
+$credentials = [
+    'email'    => $this->request->getPost('email'),
+    'password' => $this->request->getPost('password')
+];
+
+$result = auth('custom')->attempt($credentials );
+
+if ($result->isOK()) {
+    $user = $result->extraInfo();
+    echo "Login successful for: " . $user->email;
+} else {
+    echo "Login failed: " . $result->reason();
+}
+
+```
+
+Now all standard authentication methods—such as `attempt()`, `check()`, `loggedIn()`, `login()`, `loginById()`, `logout()`, `getUser()`, and `recordActiveDate()`—are fully available.

docs/getting_started/authenticators.md

@@ -17,3 +17,5 @@ Shield provides the following Authenticators:
   [HMAC SHA256 Token Authenticator](../references/authentication/hmac.md) for usage.
 - **JWT** authenticator provides stateless authentication using JSON Web Token. To use this,
   you need additional setup. See [JWT Authentication](../addons/jwt.md).
+
+In addition to the default authenticators listed above, CodeIgniter Shield allows you to build and register Custom Authenticators by implementing the `AuthenticatorInterface`, enabling completely project-specific authentication strategies (external providers, hardware or device challenges, or any other custom logic), while remaining fully compatible with Shield’s authentication lifecycle and its login/logout event system. For full implementation steps, see [Custom Authenticator](../customization/custom_authenticators.md).

mkdocs.yml

@@ -115,6 +115,7 @@ nav:
     - customization/extending_controllers.md
     - customization/integrating_custom_view_libs.md
     - customization/login_identifier.md
+    - Custom Authenticators : customization/custom_authenticators.md
   - User Management:
     - user_management/managing_users.md
     - user_management/forcing_password_reset.md