## 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!

posthog/models/filters/mixins/common.py
@cached_property
    def session(self) -> Optional[str]:
        return self._data.get(SESSION, None)
    @include_dict
    def session_to_dict(self):
        return {"session": self.session} if self.session else {}
class OffsetMixin(BaseParamMixin):
    @cached_property
    def offset(self) -> int:
        _offset = self._data.get(OFFSET)
        return int(_offset or "0")
    @include_dict
    def offset_to_dict(self):
        return {"offset": self.offset} if self.offset else {}
class CompareMixin(BaseParamMixin):
    def _process_compare(self, compare: Optional[Union[str, bool]]) -> bool:
        if isinstance(compare, bool):
            return compare
        elif isinstance(compare, str):
            return str_to_bool(compare)
        else:
            return False
    @cached_property
    def compare(self) -> bool:
        _compare = self._data.get(COMPARE, None)
        return self._process_compare(_compare)
    @include_dict
    def compare_to_dict(self):
        return {"compare": self.compare} if self.compare else {}
class DateMixin(BaseParamMixin):