make it so we can delete TaskInstructionsForEndUserModel on instance delete

spiffworkflow-backend/src/spiffworkflow_backend/models/process_instance.py

@@ -73,6 +73,7 @@ class ProcessInstanceModel(SpiffworkflowBaseDBModel):
         overlaps="active_human_tasks",
     )  # type: ignore
     message_instances = relationship("MessageInstanceModel", cascade="delete")  # type: ignore
+    task_instructions_for_end_user = relationship("TaskInstructionsForEndUserModel", cascade="delete")  # type: ignore
     process_metadata = relationship(
         "ProcessInstanceMetadataModel",
         cascade="delete",

spiffworkflow-backend/tests/spiffworkflow_backend/unit/test_process_instance_processor.py

@@ -902,3 +902,6 @@ class TestProcessInstanceProcessor(BaseTest):
         assert len(remaining_entries) == 2
         for entry in remaining_entries:
             assert entry.has_been_retrieved is True
+
+        db.session.delete(process_instance)
+        db.session.commit()