Running E2E tests resets the `config.toml` file in the root dir to default values

[josecelano]

If you run the E2E tests (./docker/bin/run-e2e-tests.sh), the config.toml file in the root dir is reset to default values. That's because the API allows admins to overwrite the file.

We should change the location for the config.toml file for that test, but it's hardcoded. I'm making some refactorings here that will allow us to easily add a new argument to change the default location for the config.toml file. For example, you could run the app with the following:

cargo run --config ./config.toml

or

TORRUST_IDX_BACK_CONFIG_PATH=./config.toml cargo run

[josecelano]

In the end, what I did was:

• I do not run the test that modifies the configuration using a shared E2E environment. That test is only executed using an isolated environment.
• I have not added that option to modify the config file's default location since I do not need it anymore. But I refactored the configuration to make it easier to add more env vars in the future (including this one) if we need it.

[josecelano]

I was wrong, we need that option anyway also for isolated environments because the config.toml file location does not change. Even if we do not use the file to setup the isolated env, the test overwrites the files on the default location.

Besides, we have to change the test

async fn it_should_allow_admins_to_update_all_the_settings() {
    let mut env = TestEnv::new();

    if !env.is_isolated() {
        // This test can't be executed in a non-isolated environment because
        // it will change the settings for all the other tests.
        return;
    }

    env.start().await;

    // ...
}

To:

    let mut env = TestEnv::new();
    env.start().await;

    if !env.is_isolated() {
        // This test can't be executed in a non-isolated environment because
        // it will change the settings for all the other tests.
        return;
    }

    // ...
}

It was not being executed at all.

So, I will add the new env var to modify the file location.

TORRUST_IDX_BACK_CONFIG_PATH=./config.toml cargo run

We can move it to the temp dir created for the test env.