audio_recordings.pm: active audio uploads

If audio files become inactive because a new file is uploaded, the new
file is marked as active and the old file is marked as not active.
This allows fastly querying events and their active upload file.
Before this change all event's audio files were found and needed to be
filtered afterwards to get a set of unique events.

install/migrate.sql

@@ -270,3 +270,10 @@ ADD COLUMN `update_event_field_content_format` TINYINT(1) UNSIGNED NOT NULL AFTE
 
 ALTER TABLE `calcms_events` 
 ADD COLUMN `listen_key` VARCHAR(100) NULL;
+
+ALTER TABLE `calcms_audio_recordings`
+ADD COLUMN `active` TINYINT(1) NOT NULL DEFAULT 0 AFTER `event_id`;
+
+ALTER TABLE `calcms`.`calcms_audio_recordings`
+ADD INDEX `active_index` (`active`);
+