Add affiliate BI query

[gsidebo]

Affiliate tracking RFC

PR #1970 added support for tracking certain user actions that occur after a user follows an affiliate link to the site. In order to actually credit our affiliates for these user actions, we will want a new BI query based on that tracking data. The query will show the accounts created and orders completed as a result of affiliate traffic.

The query should at least include the following data for each row:

• The user id and email
• The affiliate code and name
• A simple string indicating the type of action ("user_created" or "completed_order"; this will be based on whether AffiliateReferralAction.created_user_id or AffiliateReferralAction.created_order_id is set. There should not be any rows with both)
• (For completed orders) The total amount paid
• The date of the account creation or order completion (AffiliateReferralAction.created_on)

Please confirm the full list of fields with Peter and Ferdi before you start

[gsidebo]

We never created any affiliates in xpro, so there's no data to report. I'll label this as On Hold until we actually start tracking affiliate referrals