feat(balances): measure usage alerts per basis and fire on usage limits

Move alert firing into balances/usageAlerts/check as resolve → measure →
wasThresholdCrossed → send. Balance bases read the breakdown for their
denominator; usage_limit alerts read the usage-window counter of the cap
that shares their feature and filter, both sides at one now so a rolled
window measures 0 before the event. The webhook carries basis, filter and
a balance or usage_limit block, and the idempotency key includes basis,
filter and window start.

Entity subjects keep customer-scope usage window rows after deduction so
a cap inherited from the customer can fire on an entity track.

Author: charlietlamb

server/src/internal/balances/trackWebhooks/checkUsageAlerts.ts

@@ -6,10 +6,10 @@ import {
 } from "@autumn/shared";
 import type { AutumnContext } from "@/honoUtils/HonoEnv.js";
 import { buildEvaluationSubject } from "@/internal/balances/check/buildEvaluationSubject.js";
+import { checkUsageAlerts } from "@/internal/balances/usageAlerts/check/checkUsageAlerts.js";
 import { getApiCustomerBase } from "@/internal/customers/cusUtils/apiCusUtils/getApiCustomerBase.js";
 import { getApiEntityBase } from "@/internal/entities/entityUtils/apiEntityUtils/getApiEntityBase.js";
 import { checkLimitReached } from "./checkLimitReached.js";
-import { checkUsageAlerts } from "./checkUsageAlerts.js";
 import { handleThresholdReached } from "./handleThresholdReached.js";
 
 export const fireTrackWebhooks = ({
@@ -22,6 +22,7 @@ export const fireTrackWebhooks = ({
 	entityId,
 	featuresFromMutationLogs,
 	eventProperties,
+	now = Date.now(),
 }: {
 	ctx: AutumnContext;
 	oldFullSubject?: FullSubject;
@@ -32,6 +33,7 @@ export const fireTrackWebhooks = ({
 	entityId?: string;
 	featuresFromMutationLogs?: Feature[];
 	eventProperties?: Record<string, unknown> | null;
+	now?: number;
 }) => {
 	const oldFullCus = oldFullSubject
 		? fullSubjectToFullCustomer({ fullSubject: oldFullSubject })
@@ -61,8 +63,11 @@ export const fireTrackWebhooks = ({
 			ctx,
 			oldFullCus,
 			newFullCus,
+			oldFullSubject,
+			newFullSubject,
 			feature: affectedFeature,
 			entityId,
+			now,
 		}).catch((error) => {
 			ctx.logger.error(`[fireTrackWebhooks] checkUsageAlerts: ${error}`);
 		});