AIP #61 v5: Spenders & Address accounting (postgres)

[elpiel]

https://github.com/AdExNetwork/aips/issues/61

NOTE: In the database the Accounting is flatten and it was introduced in #413 . This is why we have 2 Accounting structs - one for sentry and one for the database.
When building the sentry Accounting as a response we should collect all Channel Accounting rows from the Database and produce the balances map (earners & spenders).

TODOs:

• relate the Accounting with a spender (advertiser) & ChannelId. It should include earners & spenders balances that should match, i.e. sum(earners) == sum(spenders) PR: Issue 382 campaign insert events #413
• Accounting PRs: Issue 381 Accounting - get spent amount #410 Issue 382 campaign insert events #413
  • it's own DB collection, includes channel_id and is flat structure (1 accounting = 1 earner or spender for channel)
• Spendable amounts - new collection which is unique by (channel_id, spender) and we store the { total, stillOnCreate2 } from the AIP #61 v5: Adapter - total spendable amount #380 , the collection should store { spender, channel, channel_id, total, stillOnCreate2 }