Fix LONGTEXT columns becoming TEXT in generated migrations

The issue was a mismatch between CakePHP's LENGTH_LONG constant (4294967295)
and migrations' TEXT_LONG constant (2147483647).

When using `bake migration_diff`, CakePHP's schema reflection returns
LENGTH_LONG for LONGTEXT columns, but MysqlAdapter expected TEXT_LONG.

This fix:
1. MigrationHelper: Convert LENGTH_LONG to TEXT_LONG when generating migrations
2. MysqlAdapter: Accept both constants for backward compatibility with existing
   migrations that have the wrong value

Fixes #1029

Author: dereuromark

src/Db/Adapter/MysqlAdapter.php

@@ -374,8 +374,10 @@ public function createTable(TableMetadata $table, array $columns = [], array $in
     protected function mapColumnData(array $data): array
     {
         if ($data['type'] == self::TYPE_TEXT && $data['length'] !== null) {
+            // Accept both migrations TEXT_LONG and CakePHP LENGTH_LONG for backward compatibility
+            // with migrations generated before the fix (LENGTH_TINY/MEDIUM are already equal to TEXT_TINY/MEDIUM)
             $data['length'] = match ($data['length']) {
-                self::TEXT_LONG => TableSchema::LENGTH_LONG,
+                self::TEXT_LONG, TableSchema::LENGTH_LONG => TableSchema::LENGTH_LONG,
                 self::TEXT_MEDIUM => TableSchema::LENGTH_MEDIUM,
                 self::TEXT_REGULAR => null,
                 self::TEXT_TINY => TableSchema::LENGTH_TINY,

src/View/Helper/MigrationHelper.php

@@ -18,11 +18,13 @@
 use Cake\Database\Connection;
 use Cake\Database\Driver\Mysql;
 use Cake\Database\Schema\CollectionInterface;
+use Cake\Database\Schema\TableSchema;
 use Cake\Database\Schema\TableSchemaInterface;
 use Cake\Utility\Hash;
 use Cake\Utility\Inflector;
 use Cake\View\Helper;
 use Cake\View\View;
+use Migrations\Db\Adapter\MysqlAdapter;
 use Migrations\Db\Table\ForeignKey;
 
 /**
@@ -445,6 +447,13 @@ public function getColumnOption(array $options): array
             }
         }
 
+        // Convert CakePHP's LENGTH_LONG to migrations TEXT_LONG for text columns
+        // CakePHP uses LENGTH_LONG = 4294967295, but migrations expects TEXT_LONG = 2147483647
+        // (LENGTH_TINY and LENGTH_MEDIUM have the same values as TEXT_TINY and TEXT_MEDIUM)
+        if (isset($columnOptions['limit']) && $columnOptions['limit'] === TableSchema::LENGTH_LONG) {
+            $columnOptions['limit'] = MysqlAdapter::TEXT_LONG;
+        }
+
         return $columnOptions;
     }