Once the frontend has migrated to the new generic definitions endpoint with OPT-3352, the decision- and processDefinition restServices and Services can be removed from the backend.

AT:

• decision- and processDefinition RestServices are removed
• decision- and processDefinition Services are removed 
• decision- and processDefinition Readers/Writers are altered so they call generic methods in DefinitionReader/Writer, to avoid bloating the generic reader/writer with named methods)