Unit tests

[crbelaus]

Adds unit tests for:

• ErrorTracker.
  • report/3
    • with a runtime exception
    • with a bad arithmetic error
    • with an unknown function error
    • with a throw
    • with an exit
  • resolve/1
  • unresolve/1
• Telemetry
  • verifies that events are emitted

Tests can run either on PostgreSQL or SQLite3. This is determined by the DB env var so:

• DB=postgres mix test runs the tests on PostgreSQL
• DB=sqlite mix test runs the tests on SQLite3

The CI has been also updated to run tests on both databases.

---

I've also unified the configuration under the config/ folder. And the dev/test migrations under priv/repo/.

Previously we had some configuration in the root folder and other in config/. Regarding the migrations the priv/repo/ folder is not included when publishing the package but is used in dev/test.

[odarriba]

Now that we have Telemetry in main, can we test that events are emitted too?

I saw some references on how to do it on here: https://github.com/dashbitco/broadway/blob/main/test/broadway_test.exs#L311

[crbelaus]

I've added a new test case for telemetry events! 🚀

[odarriba]

🚀