Validate GraphAddRequest using Pydantic validators

[nazywam]

Hey, while playing around with the API I've noticed that if you try to add a graph link with malformed source/target fields (like "source": "abc" the server responds with an ugly exception:

  File "/root/.cache/pypoetry/virtualenvs/yeti-9TtSrW0h-py3.10/lib/python3.10/site-packages/fastapi/routing.py", line 190, in run_endpoint_function
    return await dependant.call(**values)
  File "/app/core/web/apiv2/graph.py", line 88, in add
    source_type, source_id = request.source.split("/")
ValueError: not enough values to unpack (expected 2, got 1)

How do you feel about validating the incoming fields using pydantic validators?

This is how the response looks in comparison to the previous one:

Probably a similar approach can be used for other incoming models as well.

[tomchop]

Amazing, thanks! Do you know if we can make source and target be of a custom type with a validator, instead of setting a validator on the string? I'm thinking that I'd prefer having this sit closer to the ArangoDB model (given that type/id is an arangoDB implementation detail)

[nazywam]

Yeah, I think it should be possible, it'd probably look something like this -> https://docs.pydantic.dev/latest/concepts/types/#custom-types

I can try modyfing the PR if you'd like

[tomchop]

Changing this across the whole codebase might have other unintended side-effects. Let's merge this change as it is now. I opened #852 to track the wider changes. Thank you!!