Add scalable testing setup to Analytics configurator

Problem

The current version of the analytics configurator only has a barebones testing setup.

We currently use built-in Go testing libraries for unit tests to verify methods. What is missing is something similar to rspec like stubs and ability to test integration between layers. Something like

expect(DB).to receive(:exec).with("CREATE table ....")

post('/setup_project')

in Golang

Goal

Have a testing setup in place that is in accordance with best practices for Go-projects at Gitlab. The testing setup should be restricted to the analytics-configurator repo (e.g. unit-tests). We are not pursuing an E2E testing setup for now.

Process

We need to investigate how can we achieve acceptable level of integration (and potentially e2e) testing.