Media Domain library

This library currently contains a set of models and repositories that are common to media apps. But it can be expanded in the future to also include common use cases, as per domain layer guide.

The data and domain layer guides seem to imply that the definitions of the repositories should belong to the data layer. This would make the domain library dependent on a specific data library. In this project, the repositories are defined ( not implemented) in the domain layer. This makes the domain layer independent of external layers, and any implementation of the repositories can be used: the ones provided by the toolkit, or custom implementations provided by your project.

The reason for having a domain library is described in the architecture overview.