Feature: Provide Persistance DTO (PDTO)

[StraykerPL]

Is your feature request related to a problem? Please describe. To decouple relation between Application and Persistence layers even more, there must be provided additional class layer for entities to operate - Application layer will operate on Core models, while Persistence will operate on PDTO.

Describe the solution you'd like

• Add Pdtos folder on Persistence layer's project,
• Add mapping logic Core <-> PDTO on Persistence layer level,
• Create PDTOs for every Core entity in Pdtos folder,
• Refactor Persistance layer to use only PDTOs,
• Refactor Application layer to use only Core models,

Describe alternatives you've considered

Additional context Web Backend

[StraykerPL]

Blocked by #124

[StraykerPL]

Unblocked