When an export request message indicates the export should be CSV, we should post data to the export service in CSV format.

• If the data.format isn't json or csv, we should continue to throw an exception indicating we haven't implemented that format yet
• Build the payload for exportService.downloadExportUpload as CSV, using the library https://commons.apache.org/proper/commons-csv/   
  • We want to leverage a library here to help us with character escaping, quotes, headers, etc.
• CSV columns to include:
  • subscription_id
  • subscription_number
  • begin
  • end
  • quantity
  • capacity
  • hypervisor_capacity
  • metric_id
  • sku
  • product_name
  • service_level
  • usage
• As with the json-formatted logic, try to avoid OOM exceptions by using streams where possible

Testing:

• CSV export of subscriptions should work