Start and end balance anchors for historical account balances (#2455)

* Add kind field to valuation

* Fix schema conflict

* Add kind to valuation

* Scaffold opening balance manager

* Opening balance manager implementation

* Update account import to use opening balance manager + tests

* Update account to use opening balance manager

* Fix test assertions, usage of current balance manager

* Lint fixes

* Add Opening Balance manager, add tests to forward calculator

* Add credit card to "all cash" designation

* Simplify valuation model

* Add current balance manager with tests

* Add current balance logic to reverse calculator and plaid sync

* Tweaks to initial calc logic

* Ledger testing helper, tweak assertions for reverse calculator

* Update test assertions

* Extract balance transformer, simplify calculators

* Algo simplifications

* Final tweaks to calculators

* Cleanup

* Fix error, propagate sync errors up to parent

* Update migration script, valuation naming

test/fixtures/imports.yml

@@ -7,3 +7,8 @@ trade:
   family: dylan_family
   type: TradeImport
   status: pending
+
+account:
+  family: dylan_family
+  type: AccountImport
+  status: pending

test/fixtures/valuations.yml

@@ -1,2 +1,2 @@
-one: { }
-two: { }
+one:
+  kind: reconciliation