Replace the former unique attendee key with a normal index

This allows an attendee to have multiple sessions in the same conversation.

Signed-off-by: Joas Schilling <coding@schilljs.com>

appinfo/info.xml

@@ -16,7 +16,7 @@ And in the works for the [coming versions](https://github.com/nextcloud/spreed/m
 
 	]]></description>
 
-	<version>12.0.0-dev.5</version>
+	<version>12.0.0-dev.6</version>
 	<licence>agpl</licence>
 
 	<author>Daniel Calviño Sánchez</author>

lib/Migration/Version12000Date20210217134030.php

@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2021, Joas Schilling <coding@schilljs.com>
+ *
+ * @author Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Talk\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/**
+ * Replace the former unique attendee key with a normal index
+ * allowing an attendee to have multiple sessions in the same conversation.
+ */
+class Version12000Date20210217134030 extends SimpleMigrationStep {
+
+	/**
+	 * @param IOutput $output
+	 * @param Closure $schemaClosure The `\Closure` returns a `ISchemaWrapper`
+	 * @param array $options
+	 * @return null|ISchemaWrapper
+	 */
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+
+		$table = $schema->getTable('talk_sessions');
+		if ($table->hasIndex('ts_attendee')) {
+			$table->dropIndex('ts_attendee');
+		}
+		if (!$table->hasIndex('ts_attendee_id')) {
+			$table->addIndex(['attendee_id'], 'ts_attendee_id');
+		}
+
+		return $schema;
+	}
+}