[enh] Provide an insertion date

* When a certificate is added , we store his creation date

install/mysql.sql

@@ -784,6 +784,7 @@ CREATE TABLE `certificates` (
   `sslkey` text NOT NULL,
   `sslcrt` text NOT NULL,
   `sslchain` text NOT NULL,
+  `created_at` DATETIME DEFAULT CURRENT_TIMESTAMP,
   PRIMARY KEY (`id`),
   KEY `uid` (`uid`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

install/upgrades/3.5.0.1.sql

@@ -3,6 +3,7 @@
 
 DROP TABLE `certif_alias`;
 ALTER TABLE `certificates` DROP `shared`, DROP `ssl_action`, DROP `ssl_result`;
+ALTER TABLE `certificates` ADD `created_at` DATETIME DEFAULT CURRENT_TIMESTAMP;
 
 ALTER TABLE `sub_domaines`
       ADD `certificate_id` INT UNSIGNED NOT NULL DEFAULT '0' AFTER `enable`,