## 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/utils.py
from django.db import connection
    query = (
        f'SELECT pg_size_pretty(pg_total_relation_size(relid)) AS "size" '
        f"FROM pg_catalog.pg_statio_user_tables "
        f"WHERE relname = '{table_name}'"
    )
    cursor = connection.cursor()
    cursor.execute(query)
    return dict_from_cursor_fetchall(cursor)[0]["size"]
def get_table_approx_count(table_name) -> str:
    from django.db import connection
    query = f"SELECT reltuples::BIGINT as \"approx_count\" FROM pg_class WHERE relname = '{table_name}'"
    cursor = connection.cursor()
    cursor.execute(query)
    return compact_number(dict_from_cursor_fetchall(cursor)[0]["approx_count"])
def compact_number(value: Union[int, float]) -> str:
    """Return a number in a compact format, with a SI suffix if applicable.
    Client-side equivalent: utils.tsx#compactNumber.
    """
    value = float("{:.3g}".format(value))
    magnitude = 0
    while abs(value) >= 1000:
        magnitude += 1
        value /= 1000.0
    return "{:f}".format(value).rstrip("0").rstrip(".") + ["", "K", "M", "B", "T", "P", "E", "Z", "Y"][magnitude]
def is_postgres_alive() -> bool: