Use Ecto sandbox on tests about helix HOT 1 CLOSED

I'll defer this task.

I've worked on it for around two hours and found a blocking point:
When you setup the sandbox, anything that uses the pool depends on the ownership mechanism, so the test has to explicitly allow a certain process to use the database (by sharing ownership with them).

The problem is, events spawned by Helix.Event are processes and you can't know their pid (as it doesn't return that info), so it immediately fails the test.

I've stashed the changes. I'll take a look at this again in the future. I can see two ways to fix it:

1. Implement "Adapters" for the Event, that way we can use a different adapter on test environment and that adapter would allow us to provide allowance of use on the database for them
2. Run event tests on a separate test run that don't use sandbox

from helix.