feature: deleting a generator target object should delete the created objects of that target

[wvandeun]

Component

API Server / GraphQL

Current Behavior

It is not clear how a generator target object should be properly deleted within Infrahub.

• When you delete the target node from the target group, then the generator does not seem to delete all the objects that the generator created as a result of the target.

• When you delete the target node from Infrahub, then the generator will raise an error message.

Expected Behavior

We should have a clear and defined way to delete generator target nodes and the resulting objects.

Steps to Reproduce

• load the following schema

  ---
  version: "1.0"
  nodes:
  - name: TagService
  namespace: Test
  attributes:
    - name: name
      label: Name
      kind: Text
      optional: false
      unique: true
    - name: amount
      label: Amount
      kind: Number
      optional: false

• create a group called tag_services in Infrahub
• define a generator in an external repository

  generator_definitions:
  - name: tag_service_generator
  file_path: "test_tag_service.py"
  targets: tag_services
  query: test_tag_service
  class_name: TestTagService
  parameters:
    name: "name__value"

  query TagService($name: String!) {
  TestTagService(name__value: $name) {
  edges {
    node {
  name {
    value
  }
  amount {
    value
  }
    }
  }
  }
  }

  
  from infrahub_sdk.generator import InfrahubGenerator

class TestTagService(InfrahubGenerator): async def generate(self, data: dict) -> None: service = data["TestTagService"]["edges"][0]["node"]

    name = service["name"]["value"]
    amount = service["amount"]["value"]

    for i in range(amount):
        tag = await self.client.create(kind="BuiltinTag", name=f"{name}-{i+1}")
        await tag.save(allow_upsert=True)

- create/syn the external repository in Infrahub
- create a new branch in Infrahub
- create a TestTagService object with name test and amount 3
- add the TestTagService object to the `tag_services` group
- create a proposed change to merge the branch into main
- 3 tags will have been created
- merge the branch
- create a new branch in Infrahub
- delete the TestTagService object from the `tag_services` group
- open a proposed change for the branch
- the generator will run, but it will not delete the tag objects 
- open a new branch in Infrahub
- delete the TestTagService object
- open a proposed change for the branch
- the generator will raise an error message (and the tag object will not have been deleted)

### Additional Information

_No response_

[wvandeun]

after discussion with @ogenstad it would be better to flag this as a feature request