We are running all E2E with the same application instance. The process is as follows:

1.- Start docker containers with E2E env.
2.- Run E2E tests.
3.- Stop containers.

After merging this PR, we can run an isolated app instance for each test.

This PR allows E2E tests to be executed with isolated app instances:

• Without using docker.
• And in a way, we can mock services, setting the initial test state easier, etcetera.

For now, we can run most of the E2E tests twice: with the shared docker instance or with the isolated app instances. YOu can change the behaviour with an env var.

With the shared app (docker):

TORRUST_IDX_BACK_E2E_SHARED=true cargo test

With isolated app instance (only rust):

cargo test

Some tests cannot be executed in an isolated env because they require a running tracker. We could change them to use a mock.

In general, I would try to keep only a few E2E tests using the real tracker and most of them using the mock. In the future, we could differentiate them using a different folder. Right now, the ones that require the running tracker have this:

if !env.provides_a_tracker() {
   return
}

to skip the test when the test env does not provide a running tracker.