refactored notificatoin / tgsettle responsibility boundaries

api/proto/account_created.proto

@@ -2,7 +2,10 @@ syntax = "proto3";
 
 option go_package = "github.com/tech/sendico/pkg/generated/gmessaging";
 
+// AccountCreatedEvent is published when a new user account is registered.
 message AccountCreatedEvent {
+    // account_ref is the unique reference of the newly created account.
     string account_ref = 1;
+    // verification_token is the one-time token used to verify the email address.
     string verification_token = 2;
 }