+100 Integration tests & Clean Architecture layers

This week before releasing v1.3.0 I'll be adding more integration tests regarding Subscriptions, as it is the most requested feature.

We've been asked if we could implement Paddle (besides Stripe), and we wanted to implement it but we haven't had the time, as this is a side project.

We also divided the single project into:

src:
-Project.Domain
-Project.Application
-Project.Infrastructure
-Project.WebApi
-Project.Winforms
tests:
-Project.IntegrationTests
-Project.UnitTests

We're thinking v1.3.0 will be ready this sunday.