Add IdentityColumnsNotSupported exception

src/Driver/OCI8/Exception/IdentityColumnsNotSupported.php

+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\DBAL\Driver\OCI8\Exception;
+
+use Doctrine\DBAL\Driver\OCI8\OCI8Exception;
+
+/**
+ * @internal
+ *
+ * @psalm-immutable
+ */
+final class IdentityColumnsNotSupported extends OCI8Exception
+{
+    public static function new(): self
+    {
+        return new self('The driver does not support identity columns.');
+    }
+}

src/Driver/OCI8/OCI8Connection.php

@@ -4,7 +4,7 @@ declare(strict_types=1);
 
 namespace Doctrine\DBAL\Driver\OCI8;
 
-use Doctrine\DBAL\Driver\Connection;
+use Doctrine\DBAL\Driver\OCI8\Exception\IdentityColumnsNotSupported;
 use Doctrine\DBAL\Driver\Result as ResultInterface;
 use Doctrine\DBAL\Driver\ServerInfoAwareConnection;
 use Doctrine\DBAL\Driver\Statement as DriverStatement;
@@ -111,7 +111,7 @@ final class OCI8Connection implements Connection, ServerInfoAwareConnection
     public function lastInsertId(?string $name = null): string
     {
         if ($name === null) {
-            throw new OCI8Exception('The driver does not support identity columns.');
+            throw IdentityColumnsNotSupported::new();
         }
 
         $result = $this->query('SELECT ' . $name . '.CURRVAL FROM DUAL')->fetchOne();