[OP-19965] Fix 500 when initializing an occurrence on a draft recurring meeting template

modules/meeting/app/services/recurring_meetings/init_occurrence_service.rb

@@ -62,7 +62,8 @@ def perform
     end
 
     def draft_template_failure
-      ServiceResult.failure(message: I18n.t("recurring_meeting.occurrence.error_template_draft"))
+      recurring_meeting.errors.add(:base, I18n.t("recurring_meeting.occurrence.error_template_draft"))
+      ServiceResult.failure(errors: recurring_meeting.errors)
     end
 
     def validate_contract

modules/meeting/spec/services/recurring_meetings/init_occurrence_service_spec.rb

@@ -67,6 +67,15 @@
         expect(created_meeting).to be_nil
       end
 
+      it "carries a non-empty errors object usable by the API layer" do
+        # Regression test: draft_template_failure used to return only a
+        # message with no errors:, which crashed
+        # API::Errors::ErrorBase.create_and_merge_errors(call.errors) with an
+        # ArgumentError ("expected at least one error") when the API route
+        # tried to build a MultipleErrors response from an empty error list.
+        expect(service_result.errors).not_to be_empty
+      end
+
       it "does not add an occurrence" do
         expect { instance.call(**params) }
           .not_to change { series.meetings.not_templated.count }