adds a rake task needed by semaphore
adds a rake task needed by semaphore

based on this blog post https://blog.devartis.com/using-parallel-tests-with-semaphore-to-speed-up-rails-builds-838589a93a5

to help setup multiple databases for parallel testing.

The reason for the rake test is that semaphore seems to either use its
own database.yml file or extends our Database. Whatever it does it does
not create a DB using 'correspondence_platform_test'

```
Created database '4576c3eb-xxx_test'
Created database '4576c3eb-xxx_test2'
Created database '4576c3eb-xxx_test3'
Created database '4576c3eb-xxx_test4'
```

The rake test is called inside a semaphore job. https://semaphoreci.com/aliuk2012/correspondence_tool_staff/settings

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