MySQL doesn't allow us to create a trigger for a column that doesn't
exist yet. Failing with this error:

```
Mysql2::Error: Unknown column 'build_events' in 'NEW': CREATE TRIGGER trigger_6a80c097c862_insert
BEFORE INSERT
ON `services`
FOR EACH ROW
SET NEW.`build_events` = NEW.`job_events`
```

Creating the new column before creating the trigger avoids this.