Add support in tests for serverApiProxy

[vloss3]

Motivation / Goals

Currently, the serverApiProxy option is set to false in tests due to tests using relative baseURL, e.g. baseURL: '/api'

Requirements

Tests use serverApiProxy feature.
The mocked API uses an absolute URL.

Implementation notes

This is an issue because Vitest runs every test on a randomized port, a possible solution would be to find the current port and create an absolute URL, e.g. http://localhost:PORT/api

[fago]

fixed in #210