[Backend] Add SQL-based KVIN implementation

[kenwenzel]

Most companies use SQL databases to store their data. To simplify the implementation of LinkedFactory-based data architectures a SQL-based implementation is required.

What are our options?

• use a custom data model to store data in SQL databases
  • easier to implement
  • may not work well with existing data -> check if it is possible to provide data via views
• create a mapping layer to project existing data into the KVIN data model
  • harder to implement
  • requires some kind of SQL templates for mapping the data