Feature request/Bugfix: Added support for two part difference scale which was needed for risk-opportunity scale

Body:
- introduced difference scale (and its processing)
- changed risk_opportunity_perception.yaml to new format
- retained single scale for cognitiv_selfesteem and effects_on_work

src/process_all_waves.py

@@ -121,6 +121,17 @@ class DataPreprocessingAllWaves:
                     coalesced=False,
                 )
 
+                for part_name, alpha_value in getattr(
+                    scale_processor, "cronbachs_alpha_by_part", {}
+                ).items():
+                    subscale_column = f"{scale_processor.name}_{part_name}_mean"
+                    self._aggregate_cronbachs_alpha_values(
+                        subscale_column,
+                        alpha_value,
+                        wave_number,
+                        coalesced=False,
+                    )
+
             result_dataframe: pd.DataFrame = pd.concat(
                 [data[[participant_id_column]], *scale_dfs], axis=1
             )