Additional minutes addon purchase add sub add minutes events

[ikreymer]

• Fixes [Task]: Add new SubscriptionAddMinutes event to subscriptions #3052
• New SubscriptionAddMinutes event, added via /subscription/add-minutes endpoint, storing total_price, currency, context, oid and minutes added.
• Remove org/quotas/add endpoint (can readd if needed for superadmin use later)
• Remove 'context' from OrgQuotasIn, only added from SubscriptionAddMinutes, though keep on OrgQuotasUpdate list on orgs
• add filtering by 'add-minutes' subscription event type

[tw4l]

Code quality/changes/tests look good. I'll defer to you and Emma on the approach but good to have the subscription event and type filtering available

[emma-sg]

Looking good to me as well!