Document current domain model

[cyrildewit]

Description

When domain entities are added to the system design, they were added with a purpose and intention of how it's supposed to be used. Generic documentation about the various domain entities that describes what they represent, allows us to easily refresh our knowledge about the system. The relationships between the domain entities are pratical to document as well, because this allows us to get a good understanding of how the data is structured.

Requirements

• Add a new page called "Domain models" at "https://fhict-skilltree.github.io/backend-application/docs/technical/architecture/domain-models"
• Title: "Domain Models"
• Create an overview of all domain models including their relationships according in the form of a data model. This is unfortunely not how DDD is supposed be designed, but it will be used as a starting point to convert it to a DDD-way.