Add an API endpoint test

[Azoorb]

I find that there is a lack of a complete test example in the documentation, especially for testing an API endpoint.

Indeed, I am using multi-database tenancy with domain routing, and testing something like $this->get('/auth/login') is not straightforward because we cannot do $this->get('fakedomain.com/auth/login'), it result in a 404 response.

Perhaps adding an example in the documentation could make testing clearer.
Thank you for this great package!