Revert "fix(frontend): replace expected-origin-boundary with middleware"

This reverts commit 982bc4ba

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

frontend/src/components/layout/expected-origin-boundary.tsx

@@ -0,0 +1,44 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { headers } from 'next/headers'
+import type { PropsWithChildren } from 'react'
+import React from 'react'
+
+export interface ExpectedOriginBoundaryProps extends PropsWithChildren {
+  expectedOrigin: string
+}
+
+/**
+ * Determines the host and protocol of the current request by checking the host or x-forwarded-host header.
+ *
+ * @return the calculated request origin or {@code undefined} if no host header has been found
+ */
+export const buildOriginFromHeaders = (): string | undefined => {
+  const currentHeader = headers()
+  const host = currentHeader.get('x-forwarded-host') ?? currentHeader.get('host')
+  if (host === null) {
+    return undefined
+  }
+
+  const protocol = currentHeader.get('x-forwarded-proto')?.split(',')[0] ?? 'http'
+  return `${protocol}://${host}`
+}
+
+/**
+ * This boundary lets the given children pass if the current request origin is matching the expected origin for this route.
+ * Otherwise, an error message is shown instead.
+ *
+ * @param children the children to show if the origin passes
+ * @param expectedOrigin The origin that should match the request's origin
+ */
+export const ExpectedOriginBoundary: React.FC<ExpectedOriginBoundaryProps> = ({ children, expectedOrigin }) => {
+  const currentOrigin = buildOriginFromHeaders()
+
+  if (new URL(expectedOrigin).origin !== currentOrigin) {
+    return <span>{`You can't open this page using this URL. For this endpoint "${expectedOrigin}" is expected.`}</span>
+  }
+  return children
+}