So where does the business logic live?

Let's go back to the definition of business logic again. It defines the business requirements and rules that will be applied to the data. This includes the ways data is created, represented, and modified. To give you a short answer, according to our MVP approach, it lives in our AppBundle under the /Entity folder. However, later it will move to a couple of services (which can be kept in any folder and can be called globally from anywhere in the project).

Let me clarify the purpose of using Entity, EntityRepository, and Service in our project. Entity represents an object definition for a thing in real life (that is, workspace, project, task, or user). EntityRepository is where you define methods to do database queries (that is, using CRUD on entities). You can do the same in a Service but the difference is that a Service can be called globally anywhere in your project. Moreover, it is instantiated only once and on demand (no matter how many times...