Account Issue Model and Resolution Flow + Troubleshooting guides (#1090)

* Rough draft of issue system

* Simplify design

* Remove stale files from merge conflicts

* STI for issues

* Cleanup

* Improve Synth api key flow

* Stub api key for test

app/models/account/balance/syncer.rb

@@ -1,9 +1,6 @@
 class Account::Balance::Syncer
-  attr_reader :warnings
-
   def initialize(account, start_date: nil)
     @account = account
-    @warnings = []
     @sync_start_date = calculate_sync_start_date(start_date)
   end
 
@@ -20,6 +17,8 @@ class Account::Balance::Syncer
         account.update! balance: daily_balances.select { |db| db.currency == account.currency }.last&.balance
       end
     end
+  rescue Money::ConversionError => e
+    account.observe_missing_exchange_rates(from: e.from_currency, to: e.to_currency, dates: [ e.date ])
   end
 
   private
@@ -67,20 +66,26 @@ class Account::Balance::Syncer
       from_currency = account.currency
       to_currency = account.family.currency
 
+      if ExchangeRate.exchange_rates_provider.nil?
+        account.observe_missing_exchange_rate_provider
+        return []
+      end
+
       exchange_rates = ExchangeRate.find_rates from: from_currency,
                                                to: to_currency,
                                                start_date: sync_start_date
 
+      missing_exchange_rates = balances.map(&:date) - exchange_rates.map(&:date)
+
+      if missing_exchange_rates.any?
+        account.observe_missing_exchange_rates(from: from_currency, to: to_currency, dates: missing_exchange_rates)
+        return []
+      end
+
       balances.map do |balance|
         exchange_rate = exchange_rates.find { |er| er.date == balance.date }
-
-        raise Money::ConversionError.new("missing exchange rate from #{from_currency} to #{to_currency} on date #{balance.date}") unless exchange_rate
-
         build_balance(balance.date, exchange_rate.rate * balance.balance, to_currency)
       end
-    rescue Money::ConversionError
-      @warnings << "missing exchange rates from #{from_currency} to #{to_currency}"
-      []
     end
 
     def build_balance(date, balance, currency = nil)