JSONRequest losing headers when useGETForQueries is true

[dchohfi]

Bug report

After migrating my project to the new version, I'm not able to use a service that has authentication via header.

Versions

Please fill in the versions you're currently using:

• apollo-ios SDK version: 0.34.0
• Xcode version: 12.0.1
• Swift version: 5.3

Steps to reproduce

Create an interceptor that adds a header to the request, the NetworkTransporter must have useGETForQueries=true.

Further details

When the method toURLRequest gets called, the request gets recreated and all headers are lost, including the defaults added by apollo. After digging into the code, I found that the library is instantiating a new URLRequest instead of just changing the URL.

https://github.com/apollographql/apollo-ios/blob/main/Sources/Apollo/JSONRequest.swift#L101

[dchohfi]

I would love to send a PR to fix it, just want to confirm first if this is what is happening.