Returns the same data as the cabinet Analytics "Overview" tab for the project of the API key:
KPI numbers for the period (period), the same numbers for the previous period of equal length
(previous_period, previous_period_dates) and the chart series (overview).
from/to are interpreted in the project timezone; defaults to the last 30 days.

overview.granularity is hour when the period is shorter than 48 hours, otherwise day.
overview.series is keyed by metric id; the metric list, labels and the matching period key
(period_key) are available in catalog.overview_metrics of GET /reports/chart-builder/catalog.
For a single metric broken down by any dimension use GET /reports/chart-builder.