feat: add kubernetes_manifest interface

[NohaIhab]

This adds the kubernetes_manifest interface, as used by the Resource Dispatcher charm.

[DnPlas]

LGTM, thanks @NohaIhab. Could we get approval from @simskij as well?

[ca-scribner]

Is this kuberntes_manifest, or app? I think this level is talking about whether we're writing in unit or app space.

And then the next level down would be any named attribute inside data (so I think manifest_content)

[ca-scribner]

Are we changing this file intentionally? This looks like something that got formatted accidentally

[PietroPasotti]

FYI, you can put the field description in... the field description!

Suggested change

	manifest_content: str
	manifest_content: str = pydantic.Field(..., description="The content of the kubernetes manifest file.")

as it's technically not an arg.

[PietroPasotti]

you're supposed to have an 'unit' and/or an 'app' in here:
https://github.com/canonical/charm-relation-interfaces/blob/main/interfaces/ingress/v2/schema.py#L58

it needs to read:

class MyAppDatabag(BaseModel):
    kubernetes_manifests: List[KubernetesManifest]

class RequirerSchema(DataBagSchema):
    app: MyAppDatabag

the requirer schema represents "the requirer's side", which includes app and unit databags with their own schemas.

it's easier to think about it if you map it to show-relation's output

[PietroPasotti]

if I look at the example above in the docstring, this is not a string but a dictionary containing all sorts of data.

[ca-scribner]

We're still missing something here. Before, we had data of:

data = {
  'unit': {},  # <-- this comes from the [DataBagSchema](https://github.com/canonical/pytest-interface-tester/blob/50cd08647af9a8e1f904ed922a754460cd2027ce/interface_tester/schema_base.py#L10)
  'app': [manifest1, manifest2, ...]  # <-- this comes from your schema.py
}

Now, we have

data = {
  'unit': {},  # <-- this comes from the [DataBagSchema](https://github.com/canonical/pytest-interface-tester/blob/50cd08647af9a8e1f904ed922a754460cd2027ce/interface_tester/schema_base.py#L10)
  'app': {},  # <-- this comes from the [DataBagSchema](https://github.com/canonical/pytest-interface-tester/blob/50cd08647af9a8e1f904ed922a754460cd2027ce/interface_tester/schema_base.py#L10)
  'kubernetes_manifests: [manifest1, manifest2, ...]
}

This gets a little clearer imo if we paste the requirer.json into a json schema viewer (paste to the right hand side, then click "generate json from schema"). Note we get 3 attributes.

What I think we need here is one more class in the hierarchy. See the tracing example for what I mean (and you can paste their .json into the renderer to see the difference)

[ca-scribner]

ahh, @PietroPasotti beat me to it :D