## 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 == "cohort" and filter.breakdown_value != "all":
        events = events.filter(
            Exists(
                CohortPeople.objects.filter(
                    cohort_id=int(filter.breakdown_value), person_id=OuterRef("person_id"),
                ).only("id")
            )
        )
    return events
def _filter_person_prop_breakdown(events: QuerySet, filter: Filter) -> QuerySet:
    if filter.breakdown_type == "person":
        events = events.filter(
            Exists(
                Person.objects.filter(
                    **{"id": OuterRef("person_id"), "properties__{}".format(filter.breakdown): filter.breakdown_value,}
                ).only("id")
            )
        )
    return events
def _filter_event_prop_breakdown(events: QuerySet, filter: Filter) -> QuerySet: