Context:

In our coding conventions (https://confluence.camunda.com/display/CO/Coding+Conventions), we specify the following: 
"If possible, mapping methods to convert between RestDtos and the default Service Layer DTOs are to be implemented on the RestDto as static methods."

Currently, there are still a few mapping methods that aren't implemented on the RestDto as static methods. Lets do a refactor here to align the code with our conventions.

Hint:

This applies to *RestDto, *RequestDto, and *ResponseDto, and should cover mapping both to and from service layer Dtos. 

AT:

• Where possible, mappers are moved to their respective RestDtos as static methods