## Bug description

We've had a user create a funnel with Korean characters and 17 steps, which causes this issue:
![image](https://user-images.githubusercontent.com/1727427/120301818-8c212a00-c2cd-11eb-8b00-7ba242e4a9ab.png)

## Expected behavior

We should send requests to api/insight/funnel using POST instead of GET.

## How to reproduce

1.
2.
3.

## Environment

- [ ] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: _please provide_

## Additional context



#### *Thank you* for your bug report – we love squashing them!

posthog/api/action.py
events: Union[EventManager, QuerySet] = Event.objects.none()
    if filter.session:
        events = Event.objects.filter(team=team).filter(base.filter_events(team.pk, filter)).add_person_id(team.pk)
    else:
        if entity.type == TREND_FILTER_TYPE_ACTIONS:
            actions = Action.objects.filter(deleted=False)
            try:
                actions.get(pk=entity.id)
            except Action.DoesNotExist:
                return events
        events = base.process_entity_for_events(entity, team_id=team.pk, order_by=None).filter(
            base.filter_events(team.pk, filter, entity)
        )
    return events
def _filter_cohort_breakdown(events: QuerySet, filter: Filter) -> QuerySet: