Azure – How to return PDF content from another HttpResponseMessage to the browser?

I am in the process of creating a proxy server that makes a request to a PDF Blob link then takes the request to setup its HttpResponse Header which we sent to the client. This diagram should explain

As of now, I am successful at making the request to get the pdf content however I am not sure how to send that back to the user. I have followed other Stackoverflow post such as this one : https://stackoverflow.com/a/43232581/10541061

I turn the response message in step 3 of the diagram to a stream and sent it back in the new HttpResponseMessage content.But instead of PDF content , I get a json file

What I want to return to the client

What I am actually returning to the client

Here is the code I am using to create this proxy endpoint

        [AllowAnonymous]
        [HttpGet("openPDF")]
        public async Task<HttpResponseMessage> OpenPDF([FromQuery] string url)
        {
            var _httpClient = _httpClientFactory.CreateClient();
            var response = await _httpClient.GetAsync(url);
            var stream = await response.Content.ReadAsStreamAsync();

            HttpResponseMessage message = new HttpResponseMessage(HttpStatusCode.OK);
            message.Content = new StreamContent(stream);
            message.Content.Headers.ContentLength = stream.Length;
            message.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");

            return message;
        }

EDIT

Ok so this actually sends back the PDF when I write the proxy like this

        [AllowAnonymous]
        [HttpGet("openPDF")]
        public async Task<FileStreamResult> OpenPDF([FromQuery] string url)
        {
            var fileStream = new MemoryStream();

            var _httpClient = _httpClientFactory.CreateClient();

            var file = await _httpClient.GetStreamAsync(url).ConfigureAwait(false);
            await file.CopyToAsync(fileStream);

            fileStream.Position = 0;
            
            return File(fileStream, "application/pdf", "filename.pdf");
        }

The problem is I want to update the content-disposition to inline so I can force this to open in the browser instead of downloading.So I decided to take the filestream and injecting that in the httpResponseMessage.content instead but that still didn’t work. It would continue to send me a json file

        [AllowAnonymous]
        [HttpGet("openPDF")]
        public async Task<HttpResponseMessage> OpenPDF([FromQuery] string url)
        {
            var fileStream = new MemoryStream();

            var _httpClient = _httpClientFactory.CreateClient();

            var file = await _httpClient.GetStreamAsync(url).ConfigureAwait(false);
            await file.CopyToAsync(fileStream);

            fileStream.Position = 0;
            

            HttpResponseMessage message = new HttpResponseMessage(HttpStatusCode.OK);
            message.Content = new StreamContent(fileStream);
            message.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");

            return message;
        }

To be honest, I thought defining the content-type should suffice but guess not