collab: Add POST /billing/subscriptions/sync endpoint (#30956)

This PR adds a new `POST /billing/subscriptions/sync` endpoint that can
be used to sync a user's billing subscriptions from Stripe.

Release Notes:

- N/A

crates/collab/src/api/billing.rs

@@ -61,6 +61,10 @@ pub fn router() -> Router {
             "/billing/subscriptions/migrate",
             post(migrate_to_new_billing),
         )
+        .route(
+            "/billing/subscriptions/sync",
+            post(sync_billing_subscription),
+        )
         .route("/billing/monthly_spend", get(get_monthly_spend))
         .route("/billing/usage", get(get_current_usage))
 }
@@ -737,6 +741,73 @@ async fn migrate_to_new_billing(
     }))
 }
 
+#[derive(Debug, Deserialize)]
+struct SyncBillingSubscriptionBody {
+    github_user_id: i32,
+}
+
+#[derive(Debug, Serialize)]
+struct SyncBillingSubscriptionResponse {
+    stripe_customer_id: String,
+}
+
+async fn sync_billing_subscription(
+    Extension(app): Extension<Arc<AppState>>,
+    extract::Json(body): extract::Json<SyncBillingSubscriptionBody>,
+) -> Result<Json<SyncBillingSubscriptionResponse>> {
+    let Some(stripe_client) = app.stripe_client.clone() else {
+        log::error!("failed to retrieve Stripe client");
+        Err(Error::http(
+            StatusCode::NOT_IMPLEMENTED,
+            "not supported".into(),
+        ))?
+    };
+
+    let user = app
+        .db
+        .get_user_by_github_user_id(body.github_user_id)
+        .await?
+        .ok_or_else(|| anyhow!("user not found"))?;
+
+    let billing_customer = app
+        .db
+        .get_billing_customer_by_user_id(user.id)
+        .await?
+        .ok_or_else(|| anyhow!("billing customer not found"))?;
+    let stripe_customer_id = billing_customer
+        .stripe_customer_id
+        .parse::<stripe::CustomerId>()
+        .context("failed to parse Stripe customer ID from database")?;
+
+    let subscriptions = Subscription::list(
+        &stripe_client,
+        &stripe::ListSubscriptions {
+            customer: Some(stripe_customer_id),
+            // Sync all non-canceled subscriptions.
+            status: None,
+            ..Default::default()
+        },
+    )
+    .await?;
+
+    for subscription in subscriptions.data {
+        let subscription_id = subscription.id.clone();
+
+        sync_subscription(&app, &stripe_client, subscription)
+            .await
+            .with_context(|| {
+                format!(
+                    "failed to sync subscription {subscription_id} for user {}",
+                    user.id,
+                )
+            })?;
+    }
+
+    Ok(Json(SyncBillingSubscriptionResponse {
+        stripe_customer_id: billing_customer.stripe_customer_id.clone(),
+    }))
+}
+
 /// The amount of time we wait in between each poll of Stripe events.
 ///
 /// This value should strike a balance between:
@@ -979,18 +1050,11 @@ async fn handle_customer_event(
     Ok(())
 }
 
-async fn handle_customer_subscription_event(
+async fn sync_subscription(
     app: &Arc<AppState>,
-    rpc_server: &Arc<Server>,
     stripe_client: &stripe::Client,
-    event: stripe::Event,
-) -> anyhow::Result<()> {
-    let EventObject::Subscription(subscription) = event.data.object else {
-        bail!("unexpected event payload for {}", event.id);
-    };
-
-    log::info!("handling Stripe {} event: {}", event.type_, event.id);
-
+    subscription: stripe::Subscription,
+) -> anyhow::Result<billing_customer::Model> {
     let subscription_kind = if let Some(stripe_billing) = &app.stripe_billing {
         stripe_billing
             .determine_subscription_kind(&subscription)
@@ -1102,7 +1166,7 @@ async fn handle_customer_subscription_event(
                 user_id = billing_customer.user_id,
                 subscription_id = subscription.id
             );
-            return Ok(());
+            return Ok(billing_customer);
         }
 
         app.db
@@ -1121,6 +1185,23 @@ async fn handle_customer_subscription_event(
             .await?;
     }
 
+    Ok(billing_customer)
+}
+
+async fn handle_customer_subscription_event(
+    app: &Arc<AppState>,
+    rpc_server: &Arc<Server>,
+    stripe_client: &stripe::Client,
+    event: stripe::Event,
+) -> anyhow::Result<()> {
+    let EventObject::Subscription(subscription) = event.data.object else {
+        bail!("unexpected event payload for {}", event.id);
+    };
+
+    log::info!("handling Stripe {} event: {}", event.type_, event.id);
+
+    let billing_customer = sync_subscription(app, stripe_client, subscription).await?;
+
     // When the user's subscription changes, push down any changes to their plan.
     rpc_server
         .update_plan_for_user(billing_customer.user_id)