Deleting a collaboration should also delete linked resources

@@ -515,6 +515,12 @@ def delete(self, id):
               type: integer
             description: Collaboration id
             required: true
+          - in: query
+            name: delete_dependents
+            schema:
+              type: boolean
+            description: If set to true, the collaboratio will be deleted along
+              with all its tasks and nodes (default=False)
 
         responses:
           200:
@@ -540,6 +546,24 @@ def delete(self, id):
             return {'msg': 'You lack the permission to do that!'}, \
                 HTTPStatus.UNAUTHORIZED
 
+        if collaboration.tasks or collaboration.nodes:
+            delete_dependents = request.args.get('delete_dependents', False)
+            if not delete_dependents:
+                return {
+                    "msg": f"Collaboration id={id} has "
+                    f"{len(collaboration.tasks)} tasks and "
+                    f"{len(collaboration.nodes)} nodes. Please delete them "
+                    "separately or set delete_dependents=True"
+                }, HTTPStatus.BAD_REQUEST
+            else:
+                log.warn(f"Deleting collaboration id={id} along with "
+                         f"{len(collaboration.tasks)} tasks and "
+                         f"{len(collaboration.nodes)} nodes")
+                for task in collaboration.tasks:
+                    task.delete()
+                for node in collaboration.nodes:
+                    node.delete()
+
         collaboration.delete()
         return {"msg": f"Collaboration id={id} successfully deleted"}, \
             HTTPStatus.OK

@@ -564,6 +564,12 @@ def delete(self, id):
               minimum: 1
             description: Role id
             required: true
+          - in: query
+            name: delete_dependents
+            schema:
+              type: boolean
+            description: If set to true, the role is deleted even though users
+               with this role may lose permissions (default=False)
 
         responses:
           200:
@@ -591,6 +597,21 @@ def delete(self, id):
                 return {'msg': 'You can\'t delete a role from another '
                         'organization'}, HTTPStatus.UNAUTHORIZED
 
+        # check if role is assigned to users
+        if role.users:
+            params = request.args
+            if not params.get('delete_dependents', False):
+                return {
+                    'msg': "Role is assigned to users. Please remove the role "
+                    "from the users first, or set the 'delete_dependents' "
+                    "parameter to delete the role anyway."
+                }, HTTPStatus.BAD_REQUEST
+            else:
+                log.warn(f"Role {id} deleted even though it was assigned to "
+                         "users. This may result in missing permissions.")
+                # Note that the role is removed from the users automatically
+                # due to the relationship between the role and the user.
+
         role.delete()
 
         return {"msg": "Role removed from the database."}, HTTPStatus.OK

@@ -735,8 +735,26 @@ def delete(self, id):
             log.info(f" Removing run id={run.id}")
             run.delete()
 
+        # delete child/grandchild/... tasks
+        Task._delete_subtasks(task)
+
         # permissions ok, delete...
         task.delete()
 
         return {"msg": f"task id={id} and its algorithm run data have been "
                        "successfully deleted"}, HTTPStatus.OK
+
+    @staticmethod
+    def _delete_subtasks(task: db.Task) -> None:
+        """
+        Delete subtasks recursively.
+
+        Parameters
+        ----------
+        task : db.Task
+            Task to delete.
+        """
+        for child_task in task.children:
+            Task._delete_subtasks(child_task)
+            log.info(f" Removing child task id={child_task.id}")
+            child_task.delete()

@@ -702,6 +702,12 @@ def delete(self, id):
               type: integer
             description: User id
             required: true
+          - in: query
+            name: delete_dependents
+            schema:
+              type: boolean
+            description: If set to true, the user will be deleted along with
+              all tasks they created (default=False)
 
         responses:
           200:
@@ -728,6 +734,22 @@ def delete(self, id):
                     return {'msg': 'You lack the permission to do that!'}, \
                         HTTPStatus.UNAUTHORIZED
 
+        # check if user created any tasks
+        if user.created_tasks:
+            params = request.args
+            if not params.get('delete_dependents', False):
+                return {
+                    "msg": f"User has created {len(user.created_tasks)} tasks."
+                    " Please delete those first, or set the "
+                    "`delete_dependents` parameter to true to delete them "
+                    "automatically together with this user."
+                }, HTTPStatus.BAD_REQUEST
+            else:
+                log.warn(f"Deleting {len(user.created_tasks)} tasks created by"
+                         f" user id={id}")
+                for task in user.created_tasks:
+                    task.delete()
+
         user.delete()
         log.info(f"user id={id} is removed from the database")
         return {"msg": f"user id={id} is removed from the database"}, \