## 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
if filter.breakdown_type == "event":
        events = events.filter(**{"properties__{}".format(filter.breakdown): filter.breakdown_value,})
    return events
def calculate_people(team: Team, events: QuerySet, filter: Filter, use_offset: bool = True) -> QuerySet:
    events = events.values("person_id").distinct()
    events = _filter_cohort_breakdown(events, filter)
    events = _filter_person_prop_breakdown(events, filter)
    events = _filter_event_prop_breakdown(events, filter)
    people = Person.objects.filter(
        team=team,
        id__in=[p["person_id"] for p in (events[filter.offset : filter.offset + 100] if use_offset else events)],
    )
    people = people.prefetch_related(Prefetch("persondistinctid_set", to_attr="distinct_ids_cache"))
    return people
@receiver(post_save, sender=Action, dispatch_uid="hook-action-defined")
def action_defined(sender, instance, created, raw, using, **kwargs):
    """Trigger action_defined hooks on Action creation."""
    if created:
        raw_hook_event.send(
            sender=None,
            event_name="action_defined",
            instance=instance,
            payload=ActionSerializer(instance).data,
            user=instance.team,
        )
class LegacyActionViewSet(ActionViewSet):
    legacy_team_compatibility = True