fix: disallow updating isActive for permanent subscriptions

Author: tejasbadadare

target_chains/ethereum/contracts/contracts/pulse/scheduler/Scheduler.sol

@@ -404,6 +404,11 @@ abstract contract Scheduler is IScheduler, SchedulerState {
             revert IllegalPermanentSubscriptionModification();
         }
 
+        // Cannot deactivate a permanent subscription
+        if (!newParams.isActive) {
+            revert IllegalPermanentSubscriptionModification();
+        }
+
         // Cannot remove price feeds from a permanent subscription
         if (newParams.priceIds.length < currentParams.priceIds.length) {
             revert IllegalPermanentSubscriptionModification();

target_chains/ethereum/contracts/forge-test/PulseScheduler.t.sol

@@ -621,6 +621,16 @@ contract SchedulerTest is Test, SchedulerEvents, PulseTestUtils {
             );
             scheduler.updateSubscription(subscriptionId, updatedParams);
         }
+
+        // Test 10: Cannot deactivate a permanent subscription
+        updatedParams = storedParams;
+        updatedParams.isActive = false;
+        vm.expectRevert(
+            abi.encodeWithSelector(
+                IllegalPermanentSubscriptionModification.selector
+            )
+        );
+        scheduler.updateSubscription(subscriptionId, updatedParams);
     }
 
     function testMakeExistingSubscriptionPermanent() public {