PDFTron CustomHeader Issue

When serving PDF files with range processing enabled a HEAD request will be sent before downloading the PDF file in chunks. But when setting customHeaders, the HEAD request does not send those.

Prerequisite

• dotnet SDK 6.0.101 (https://dotnet.microsoft.com/en-us/download/dotnet/6.0)
• nodejs latest LTS 16.13.2 (https://nodejs.org/en/download/)
• add license to app.component.ts => INSERT_LICENCE_HERE

Reproducing the issue

• navigate to ./client
• execute npm ci && npm start
• navigate to ./server
• execute dotnet run
• open http://localhost:4200

=> in the devtools you'll see the HEAD request fail with status 401, due to missing headers in the request.