collab: Subscribe to Zed Free when a subscription is canceled or paused (#30965)

This PR makes it so that when a Stripe subscription is canceled or
paused we'll subscribe the user to Zed Free.

Release Notes:

- N/A

crates/collab/src/api/billing.rs

@@ -1185,6 +1185,21 @@ async fn sync_subscription(
             .await?;
     }
 
+    if let Some(stripe_billing) = app.stripe_billing.as_ref() {
+        if subscription.status == SubscriptionStatus::Canceled
+            || subscription.status == SubscriptionStatus::Paused
+        {
+            let stripe_customer_id = billing_customer
+                .stripe_customer_id
+                .parse::<stripe::CustomerId>()
+                .context("failed to parse Stripe customer ID from database")?;
+
+            stripe_billing
+                .subscribe_to_zed_free(stripe_customer_id)
+                .await?;
+        }
+    }
+
     Ok(billing_customer)
 }