feat(analytics): add behavior and payment funnel tracking

src/lib/analytics/__tests__/payment_analytics_context.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  getDefaultPaymentAnalyticsContext,
+  parsePaymentAnalyticsContext,
+} from "../payment_analytics_context";
+
+describe("payment analytics context", () => {
+  it("keeps supported payment entry and reason values", () => {
+    expect(
+      parsePaymentAnalyticsContext({
+        entryPoint: "chat_unlock",
+        triggerReason: "ad_landing",
+        subscriptionType: "topup",
+      }),
+    ).toEqual({
+      entryPoint: "chat_unlock",
+      triggerReason: "ad_landing",
+    });
+  });
+
+  it("falls back independently for invalid query values", () => {
+    expect(
+      parsePaymentAnalyticsContext({
+        entryPoint: "unsafe-entry",
+        triggerReason: "unsafe-reason",
+        subscriptionType: "topup",
+      }),
+    ).toEqual(getDefaultPaymentAnalyticsContext("topup"));
+
+    expect(
+      parsePaymentAnalyticsContext({
+        entryPoint: "sidebar",
+        triggerReason: null,
+        subscriptionType: "vip",
+      }),
+    ).toEqual({ entryPoint: "sidebar", triggerReason: "vip_cta" });
+  });
+});