Add a journey router for USSD flows

Author: HawkiesZA

Onboarding/QA/flows_ussd/md/journey-router.md

@@ -0,0 +1,28 @@
+# Router
+
+This is the main router for this Channel. When an SMS is sent on the SMS channel, it updates a contact field, which is synced to this channel. Then when the user dials into the USSD line, we check that contact field to know which journey they should be sent on.
+
+```stack
+trigger(on: "MESSAGE RECEIVED") when has_any_exact_phrase(event.message.text.body, ["0", "hi"])
+
+```
+
+<!-- { section: "ef4ebe3e-5431-460e-8017-2dfd2a8aaec7", x: 0, y: 0} -->
+
+```stack
+card Router when contact.route_to_journey == "sbm" do
+  run_stack("c151e915-7070-4682-a101-82824954a12f")
+end
+
+card Router when contact.route_to_journey == "dma" do
+  run_stack("75acc332-9d46-4a92-baf8-ae3ebf8448c2")
+end
+
+card Router do
+  # Default - no route found - run DMA - TODO: This should probably change to a menu when we get there.
+  log("No route found on contact: @contact.route_to_journey. Routing to DMA.")
+
+  run_stack("75acc332-9d46-4a92-baf8-ae3ebf8448c2")
+end
+
+```