plugin support for Model.objects.extra

[asottile-sentry]

this is similar to .annotate but slightly different / more manual querying

an example from some sentry code:

        commit_results = list(
            Commit.objects.extra(
                select={"group_id": "sentry_grouplink.group_id"},
                tables=["sentry_grouplink"],
                where=[
                    "sentry_grouplink.linked_id = sentry_commit.id",
                    "sentry_grouplink.group_id IN ({})".format(
                        ", ".join(str(i.id) for i in resolved_groups)
                    ),
                    "sentry_grouplink.linked_type = %s",
                    "sentry_grouplink.relationship = %s",
                ],
                params=[int(GroupLink.LinkedType.commit), int(GroupLink.Relationship.resolves)],
            )
        )
        _commit_resolutions = {
            i.group_id: d for i, d in zip(commit_results, serialize(commit_results, user))   # error here
        }

would probably be pretty tricky to get the exact types out -- but at the very least I would rather have mypy understand that group_id attribute exists

[sobolevn]

I agree, very cool feature! We can start small: with adding extra attributes that users define in the query with Any as the type.