fix: Revert deletion of getLocaleFromRequest in #11534 (#11835)

packages/lib/getLocaleFromRequest.ts

@@ -0,0 +1,22 @@
+/* eslint-disable @typescript-eslint/no-var-requires */
+import parser from "accept-language-parser";
+import type { GetServerSidePropsContext, NextApiRequest } from "next";
+
+import { getServerSession } from "@calcom/features/auth/lib/getServerSession";
+import type { Maybe } from "@calcom/trpc/server";
+
+const { i18n } = require("@calcom/config/next-i18next.config");
+
+export async function getLocaleFromRequest(
+  req: NextApiRequest | GetServerSidePropsContext["req"]
+): Promise<string> {
+  const session = await getServerSession({ req });
+  if (session?.user?.locale) return session.user.locale;
+  let preferredLocale: string | null | undefined;
+  if (req.headers["accept-language"]) {
+    preferredLocale = parser.pick(i18n.locales, req.headers["accept-language"], {
+      loose: true,
+    }) as Maybe<string>;
+  }
+  return preferredLocale ?? i18n.defaultLocale;
+}