Implementation of the backend for the OAuth2 clients management

api/modules/oauth/exceptions/InvalidOauthClientState.php

@@ -0,0 +1,8 @@
+<?php
+namespace api\modules\oauth\exceptions;
+
+use yii\base\Exception;
+
+class InvalidOauthClientState extends Exception implements OauthException {
+
+}

api/modules/oauth/exceptions/OauthException.php

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+<?php
+declare(strict_types=1);
+
+namespace api\modules\oauth\exceptions;
+
+interface OauthException {
+}

api/modules/oauth/exceptions/UnsupportedOauthClientType.php

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+<?php
+namespace api\modules\oauth\exceptions;
+
+use Throwable;
+use yii\base\Exception;
+
+class UnsupportedOauthClientType extends Exception implements OauthException {
+
+    /**
+     * @var string
+     */
+    private $type;
+
+    public function __construct(string $type, int $code = 0, Throwable $previous = null) {
+        parent::__construct('Unsupported oauth client type', $code, $previous);
+        $this->type = $type;
+    }
+
+    public function getType(): string {
+        return $this->type;
+    }
+
+}