EnvVarSerializer validators unique together

[deoktr]

EnvVarSerializer validators unique together on buildoptions and variable.

There is a UniqueTogetherValidator that is not in use because it cause problemes because the buildoptions is set during the perform_create on the view and not on the validate of the serializer and thus causes a bug when creating an EnvVar from the API.

validators = [
    UniqueTogetherValidator(
        queryset=EnvVar.objects.all(),
        fields=["buildoptions", "variable"],
    )
]

The constraint is present at the model level (UniqueConstraint inside EnvVar model) and thus causes an error whenever someone tries to create a duplicate envvar for the same dapp, but this error is not reflected (without the UniqueTogetherValidator validator on the serializer) and send a 500 error wich is clearly not what we want.

Implementation idea

We could add a validation on create on the EnvVarViewSet ? This add the problems of relying on the views to make the serializer validation.