## 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!

ee/clickhouse/views/insights.py
@cached_function()
    def calculate_trends(self, request: Request) -> Dict[str, Any]:
        team = self.team
        filter = Filter(request=request)
        if filter.insight == INSIGHT_STICKINESS or filter.shown_as == TRENDS_STICKINESS:
            stickiness_filter = StickinessFilter(
                request=request, team=team, get_earliest_timestamp=get_earliest_timestamp
            )
            result = ClickhouseStickiness().run(stickiness_filter, team)
        else:
            trends_query = ClickhouseTrends()
            result = trends_query.run(filter, team)
        self._refresh_dashboard(request=request)
        return {"result": result}
    @cached_function()
    def calculate_session(self, request: Request) -> Dict[str, Any]: