## 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/constants.py
SHOWN_AS = "shown_as"
FILTER_TEST_ACCOUNTS = "filter_test_accounts"
BREAKDOWN_TYPE = "breakdown_type"
BREAKDOWN_VALUE = "breakdown_value"
COMPARE = "compare"
INSIGHT = "insight"
SESSION = "session"
BREAKDOWN = "breakdown"
FROM_DASHBOARD = "from_dashboard"
PATH_TYPE = "path_type"
RETENTION_TYPE = "retention_type"
TOTAL_INTERVALS = "total_intervals"
SELECTED_INTERVAL = "selected_interval"
START_POINT = "start_point"
TARGET_ENTITY = "target_entity"
RETURNING_ENTITY = "returning_entity"
OFFSET = "offset"
PERIOD = "period"
STICKINESS_DAYS = "stickiness_days"
FORMULA = "formula"
ENTITY_ID = "entity_id"
ENTITY_TYPE = "entity_type"
ENTITY_MATH = "entity_math"
FUNNEL_WINDOW_DAYS = "funnel_window_days"
FUNNEL_FROM_STEP = "funnel_from_step"
FUNNEL_TO_STEP = "funnel_to_step"
FUNNEL_STEP = "funnel_step"
FUNNEL_ORDER_TYPE = "funnel_order_type"
FUNNEL_VIZ_TYPE = "funnel_viz_type"
class FunnelOrderType(str, Enum):