routeNextRequest.ts

import { NextRequest, NextResponse } from 'next/server';

export async function POST(req: NextRequest) {
  const body = await req.json(); // $ Source

  new NextResponse(body, {headers: { 'Content-Type': 'application/json' }});
  new NextResponse(body, {headers: { 'Content-Type': 'text/html' }});  // $ Alert
  
  const headers2 = new Headers(req.headers);
  headers2.append('Content-Type', 'application/json');
  new NextResponse(body, { headers: headers2 });

  const headers3 = new Headers(req.headers);
  headers3.append('Content-Type', 'text/html');
  new NextResponse(body, { headers: headers3 }); // $ Alert

  const headers4 = new Headers({
      ...Object.fromEntries(req.headers),
      'Content-Type': 'application/json'
  });
  new NextResponse(body, { headers: headers4 });

  const headers5 = new Headers({
      ...Object.fromEntries(req.headers),
      'Content-Type': 'text/html'
  });
  new NextResponse(body, { headers: headers5 }); // $ Alert

  const headers = new Headers(req.headers);
  headers.set('Content-Type', 'text/html');
  return new NextResponse(body, { headers }); // $ Alert
}