Add Enum class representing OAuth2 Grant Types.

Author: Potherca

src/Enum/OAuth2/GrantType.php

@@ -0,0 +1,49 @@
+<?php declare(strict_types=1);
+
+namespace Pdsinterop\Solid\Auth\Enum\OAuth2;
+
+/**
+ * Enum class representing valid values for Grant Types
+ *
+ * The values are taken ad-verbatim from RFC6749, they are used as identifiers
+ * by the League OAuth2 Server and Client libraries.
+ *
+ * Any advise whether or not to use specific grants is taken directly from the
+ * OAuth 2.0 Security Best Current Practices:
+ * https://tools.ietf.org/html/draft-ietf-oauth-security-topics
+ */
+class GrantType
+{
+    /**
+     * RFC6749 - OAuth2: Authorization Code Grant
+     * RFC7636 - Proof Key for Code Exchange (PKCE)
+     *
+     * It is recommended that all clients use the PKCE extension with this flow
+     * as well to provide better security.
+     */
+    public const AUTH_CODE = 'authorization_code';
+
+    // RFC6749 - OAuth2: Client Credentials Grant
+    public const CLIENT_CREDENTIALS = 'client_credentials';
+
+    // RFC8628: OAuth 2.0 Device Authorization Grant
+    public const DEVICE_CODE = "urn:ietf:params:oauth:grant-type:device_code";
+
+    /**
+     * RFC6749 - OAuth2: Implicit Grant
+     *
+     * @deprecated Please use Authorization Code flow with PKCE instead!
+     */
+    public const IMPLICIT = 'implicit';
+
+    /**
+     * RFC6749 - OAuth2: Resource Owner Password Credentials Grant
+     *
+     * @deprecated
+     */
+    public const PASSWORD = 'password';
+
+    // RFC6749 - OAuth2: Refresh Token Grant
+    public const REFRESH_TOKEN = 'refresh_token';
+
+}