Introduce histograms

[pierre]

This would be useful for graphs with spaced points (e.g. once a month) like:

[pierre]

Note that a current workaround is to use the smoothing functions -- maybe we could enable them automatically by default in such cases instead?

AVERAGE_MONTHLY:

SUM_MONTHLY:

[pierre]

Another work-around is to add one point per day in the report query (when the base view has one point per month):

  select
    x.tenant_record_id
  , x.slug
  , cal.d day
  , x.count
  from calendar cal
  join (
    select
      tenant_record_id
    , slug
    , day
    , sum(mrr) count
    from
      report_subscriptions_lifetime
    where 1=1
    group by 1,2,3
  ) x on last_day(cal.d) = x.day
  where 1=1
  ;