add system architecture template

fi1/README.md

@@ -138,9 +138,11 @@ Implementation notes:
 * Idempotency matters, both externally as well as internally. Never assume exactly-once delivery of a message, test extensively with non-zero delivery error rate scenarios.
 * Avoid synchronous communication with the actors requesting changes - e.g. if using HTTP - don't make clients wait for us to do any processing before we can issue an HTTP response. Store the intent and process later rather than processing in place.
 
+![system architecture template](./system_architecture_template.svg)
 
 ## Example processes - modeling and notes
 To be able to validate the system template and choose specific components from it let's analyse the processes we know of and see how easy it is to implement them.
+Would be good to draw sequence diagrams to try to understand different processes.
 
 (I ran out of time here, but based on my intuition/experience the template should still work)