fix: Merging converters

[ewuerger]

No description provided.

[micha91]

To my understanding, this PR merges add_attributes serializer configs when it comes to hierarchical configurations. I don't think that we should do that, because we loose this way the ability to define that an attribute in some cases might not be wanted in a specific type. If we want to be able to stack configurations, we should do it differently. We could for example allow configurations like this:

"*":
    "*":
      serializer:
        add_attributes-general:
          - capella_attr: layer
            polarion_id: layer
sa:
    PhysicalComponent:
      serializer:
        add_attributes:
          - capella_attr: nature
            polarion_id: nature

The general rule would be that the serializer can be suffixed using a -<suffix>. These serializers could on lower level be overwritten as they are currently overwritten, but you can also have multiple configurations of the same serializer in your config. This would also enable you to define an add_jinja_fields serializer on a on abstract level and another one as add_jinja_fields-custom on a specific level, if you want to add another custom field