blueprint: Updated blueprints to support optional actions where other actions are occuring

Author: BottlecapDave

_docs/blueprints/octopus_energy_octoplus_join_saving_session_custom_action.yaml

@@ -17,6 +17,7 @@ blueprint:
     actions:
       name: Actions
       description: Notifications or similar to be run. {{message}} is an example message
+      default: []
       selector:
         action: {}
     minimum_awarded_points:

_docs/blueprints/octopus_energy_octoplus_redeem_points_for_account_credit.yaml

@@ -26,6 +26,7 @@ blueprint:
     actions:
       name: Actions
       description: Notifications or similar to be run. {{message}} is an example message when redemption is successful
+      default: []
       selector:
         action: {}
 mode: single