Tests

I set up tests for the API endpoints using Alba. They try to simulate the actual API requests as faithfully as possible. I believe that for this project this kind of testing is more suitable than unit testing.

The tests must run against a real Postgres instance. Each test run creates its own schema in the DB. CI is configured to spawn its own Postgres container that is deleted once CI finishes to avoid polluting the main Postgres instance. The first endpoints to tests are those from the Accounts group. I already found a bug with (lack of) email validation when creating a new account.