Add security prices provider (Synth integration) (#1039)

* User tickers as primary lookup symbol instead of isin

* Add security price provider

* Fetch security prices in bulk to improve sync performance

* Fetch prices in bulk, better mocking for tests

db/migrate/20240731191344_change_primary_identifier_for_security.rb

@@ -0,0 +1,7 @@
+class ChangePrimaryIdentifierForSecurity < ActiveRecord::Migration[7.2]
+  def change
+    rename_column :securities, :symbol, :ticker
+    remove_column :securities, :isin, :string
+    rename_column :security_prices, :isin, :ticker
+  end
+end