## 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/decorators.py
from datetime import datetime
from enum import Enum
from functools import wraps
from typing import Callable, Dict, List, Union, cast
from django.core.cache import cache
from django.http.request import HttpRequest
from django.utils.timezone import now
from posthog.models import Filter, Team, User
from posthog.models.dashboard_item import DashboardItem
from posthog.models.filters.utils import get_filter
from posthog.settings import TEMP_CACHE_RESULTS_TTL
from posthog.utils import generate_cache_key
from .utils import generate_cache_key, get_safe_cache
class CacheType(str, Enum):
    TRENDS = "Trends"
    FUNNEL = "Funnel"
    RETENTION = "Retention"
    SESSION = "Session"
    STICKINESS = "Stickiness"
    PATHS = "Path"
def cached_function():