API: generate /api/state documentation from UI types (#32431)

Co-authored-by: Michael Geers <michael@geers.tv>

tests/state-api.spec.ts

@@ -0,0 +1,28 @@
+import { test, expect } from "@playwright/test";
+import { start, stop, baseUrl } from "./evcc";
+import { validateState } from "../scripts/state-schema/validate";
+
+test.use({ baseURL: baseUrl() });
+
+const CONFIG = "cmd/demo.yaml";
+
+test.beforeAll(async () => {
+  await start(CONFIG);
+});
+test.afterAll(async () => {
+  await stop();
+});
+
+test("/api/state matches the openapi State schema", async ({ request }) => {
+  // loadpoint values appear over the first update cycles, poll until stable
+  await expect
+    .poll(
+      async () => {
+        const res = await request.get("/api/state");
+        const { errors, undocumented } = validateState(await res.json());
+        return [...errors, ...undocumented];
+      },
+      { timeout: 30000 }
+    )
+    .toEqual([]);
+});