Update to use x-host header (#53780)

Author: heiskr

src/archives/middleware/archived-enterprise-versions.ts

@@ -227,16 +227,18 @@ export default async function archivedEnterpriseVersions(
     // old Azure Blob Storage URL. These need to be rewritten to
     // the new archived enterprise repo URL.
     if (versionSatisfiesRange(requestedVersion, `>=${firstReleaseStoredInBlobStorage}`)) {
+      // `x-host` is a custom header set by Fastly.
+      // GLB automatically deletes the `x-forwarded-host` header.
+      const host = req.get('x-host') || req.get('x-forwarded-host') || req.get('host')
       r.body = r.body
         .replaceAll(
           `${OLD_AZURE_BLOB_ENTERPRISE_DIR}/${requestedVersion}/assets/cb-`,
           `${ENTERPRISE_GH_PAGES_URL_PREFIX}${requestedVersion}/assets/cb-`,
         )
         .replaceAll(
           `${OLD_AZURE_BLOB_ENTERPRISE_DIR}/${requestedVersion}/`,
-          `${req.protocol}://docs.github.com/enterprise-server@${requestedVersion}/`,
+          `${req.protocol}://${host}/enterprise-server@${requestedVersion}/`,
         )
-      // TODO host: req.get('x-forwarded-host') || req.get('host')
     }
 
     // Releases 3.1 and lower were previously hosted in the