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

.gitignore

@@ -11,6 +11,7 @@
 /.env*
 !/.env*.erb
 !.env.example
+!.env.test.example
 
 # Ignore all logfiles and tempfiles.
 /log/*