Fix column size to work with Oracle. Add unit tests

Signed-off-by: Vitor Mattos <vitor@php.rio>

core/Migrations/Version24000Date20211222112246.php

@@ -71,19 +71,19 @@ class Version24000Date20211222112246 extends SimpleMigrationStep {
 				'length' => 11,
 				'unsigned' => true,
 			]);
-			$table->addColumn('actor_type', 'string', [
+			$table->addColumn('actor_type', Types::STRING, [
 				'notnull' => true,
 				'length' => 64,
 				'default' => '',
 			]);
-			$table->addColumn('actor_id', 'string', [
+			$table->addColumn('actor_id', Types::STRING, [
 				'notnull' => true,
-				'length' => 255,
+				'length' => 64,
 				'default' => '',
 			]);
 			$table->addColumn('reaction', Types::STRING, [
 				'notnull' => true,
-				'length' => 2,
+				'length' => 32,
 			]);
 			$table->setPrimaryKey(['id']);
 			$table->addIndex(['reaction'], 'comment_reaction');