As a user, I want the overview page to show a message indicating that Cost management is waiting for/processing data for my source. (Either for a newly added source or the first of the month when report data is not available.) That is, instead of viewing multiple cards, all with empty charts.

Similar to the `active` flag, used by the inactive sources feature, we would like the sources API to return a flag indicating source data is available for the current month. Thus, we wouldn't need to generate multiple report requests only to have empty data returned.

Below is a mock showing some empty states we would like to display in the UI.

https://marvelapp.com/prototype/9404edb/screen/74151763

https://marvelapp.com/prototype/9404edb/screen/74204817

FYI, the details pages infer that the cost API returns an empty data array because Cost Management is processing data; although, this may not always be a correct assumption. This is more difficult to do for the overview page because each card makes multiple requests to different APIs, in addition to requesting the current and previous months data.

A sources API flag would simplify all this and allow the overview to display custom messages for each tab and perspective option, since a source is associated with each of these types.

Acceptance Criteria:

• Boolean flag (current_month_data) added to /sources response.
  • True: At least one report manifest for current billing period has completed processing (CostUsageReportManifest.manifest_completed_datetime)