refactor: /v1/trainings/upcoming-dates sends response with trainingID and list of dates together

api/v1/openapi.yaml

@@ -255,13 +255,13 @@ paths:
 
   /v1/trainings/upcoming-dates:
     get:
-      summary: List all dates of a training
+      summary: List all upcoming dates of all trainings
       operationId: listAllUpcomingTrainingDates
       tags:
         - Trainings
       responses:
         "200":
-          description: List of training upcoming dates
+          description: List of all training upcoming dates
           content:
             application/json:
               schema:
@@ -400,7 +400,17 @@ components:
     ListAllUpcomingTrainingDatesResponse:
       type: array
       items:
-        $ref: "#/components/schemas/TrainingDate"
+        type: object
+        properties:
+          trainingID:
+            $ref: "#/components/schemas/TrainingID"
+          dates:
+            type: array
+            items:
+              $ref: "#/components/schemas/TrainingDate"
+        required:
+          - trainingID
+          - dates
 
     ListTrainingUpcomingDatesResponse:
       type: array