## Is your feature request related to a problem?

#4947 added a new query to the backend – time to convert. It works well, just one point is kind of rough: bin width and count.

## Describe the solution you'd like

Currently the number of bins is hardcoded. Ideally we should have two options:
- return a user-specified number of bins,
- otherwise infer a reasonable number of bins using some algorithm (auto option).

@alexkim205 [suggested](https://github.com/PostHog/posthog/issues/4855#issuecomment-872423877) the [Freedman-Diaconis rule](https://en.wikipedia.org/wiki/Freedman%E2%80%93Diaconis_rule) for determining bin width (and interval based on that), but unfortunately from my testing its formula would not be the most practical – it's great for keeping a pretty constant "smoothness" of the histogram esp. with normal distribution, but we face some additional constraints that make it less than ideal:
- we can't have histograms too dense visually in the UI, from my testing a practical limit is 60 bins (above that it gets too dense),
- our data generally doesn't follow much of a normal distribution.

Clamping may help though, or maybe a different formula may work better outright – I'll be testing this.

## Additional context

Issue pertaining to the experience of time to convert: #4855

#### *Thank you* for your feature request – we love each and every one!

ee/clickhouse/queries/funnels/funnel_time_to_convert.py
from ee.clickhouse.queries.funnels.funnel import ClickhouseFunnel
class ClickhouseFunnelTimeToConvert(ClickhouseFunnel):
    def _format_results(self, results: list) -> list:
        return results
    def get_query(self, format_properties) -> str:
        steps_per_person_query = self._get_steps_per_person_query()
        
        to_step = self._filter.funnel_to_step
        
        number_of_bins = 10
        if not (0 < to_step < len(self._filter.entities)):
            raise ValueError(
                f'Filter parameter funnel_to_step can only be one of {", ".join(map(str, range(1, len(self._filter.entities))))} for time to convert!'
            )