Returns cost in USD, number of requests and number of tokens per user, grouped by subscriber email (the email address sent with each call when it is metered), split into time buckets (hourly, daily or monthly, depending on the length of the date range). By default this returns coding assistant cost only. Pass costSources to include other usage. Each user has three metrics per bucket, told apart by metricType. Calls with no subscriber email are left out. For one figure per group over the whole period, a far smaller answer over a long date range, use get_cost_by_user_aggregated.