Fix column collation not applied for uuid type

The MysqlSchemaDialect in cakephp/database only adds COLLATE for
text, char, and string types. Since uuid columns generate CHAR(36)
but use the 'uuid' type identifier, collation was being ignored.

This fix converts uuid to char(36) in mapColumnData() so the dialect
properly handles the collation.

Fixes the issue reported in #1020.

Author: dereuromark

src/Db/Adapter/MysqlAdapter.php

@@ -274,6 +274,13 @@ public function createTable(Table $table, array $columns = [], array $indexes =
      */
     protected function mapColumnData(array $data): array
     {
+        // Convert uuid to char(36) to ensure collation support.
+        // The dialect only adds COLLATE for text, char, and string types.
+        if ($data['type'] === self::PHINX_TYPE_UUID) {
+            $data['type'] = 'char';
+            $data['length'] = 36;
+        }
+
         if ($data['type'] == self::PHINX_TYPE_TEXT && $data['length'] !== null) {
             $data['length'] = match ($data['length']) {
                 self::TEXT_LONG => TableSchema::LENGTH_LONG,

tests/TestCase/Db/Adapter/MysqlAdapterTest.php

@@ -166,6 +166,29 @@ public function testCreateTable()
         $this->assertFalse($columns[0]->isSigned());
     }
 
+    public function testCreateTableWithColumnCollation()
+    {
+        $table = new Table\Table('custom_collation', ['id' => false, 'primary_key' => ['id'], 'collation' => 'utf8mb4_unicode_ci']);
+
+        $columnId = new Column();
+        $columnId
+            ->setName('id')
+            ->setType('uuid')
+            ->setCollation('ascii_general_ci')
+            ->setEncoding('ascii');
+        $columnName = new Column();
+        $columnName
+            ->setName('name')
+            ->setType('text');
+        $columns = [$columnId, $columnName];
+
+        $this->adapter->createTable($table, $columns);
+
+        $rows = $this->adapter->fetchAll('SHOW FULL COLUMNS FROM custom_collation');
+        $this->assertEquals('ascii_general_ci', $rows[0]['Collation']); // specified collation is set
+        $this->assertEquals('utf8mb4_unicode_ci', $rows[1]['Collation']); // if not specified uses table's collation
+    }
+
     public function testCreateTableWithComment()
     {
         $tableComment = 'Table comment';