Fix setting wait_timeout for database

[MAILPOET-2243]

lib/Doctrine/ConnectionFactory.php

@@ -43,7 +43,9 @@ class ConnectionFactory {
     $driver_options = [
       "@@session.time_zone = '$timezone_offset'",
       '@@session.sql_mode = REPLACE(@@sql_mode, "ONLY_FULL_GROUP_BY", "")',
-      "@@session.wait_timeout = GREATEST(@@wait_timeout, $this->min_wait_timeout)",
+      // We need to use CONVERT for MySQL 8, Maria DB bug which triggers #1232 - Incorrect argument type to variable 'wait_timeout`
+      // https://stackoverflow.com/questions/35187378/mariadb-type-error-when-setting-session-variable
+      "@@session.wait_timeout = GREATEST(CONVERT(COALESCE(@@wait_timeout, 0), SIGNED), $this->min_wait_timeout)",
     ];
 
     if (!empty(Env::$db_charset)) {