Library uses wrong User-Agent in HttpServiceInterceptorInterface

[akirmse]

Environment

• Android OS version: all
• Devices affected: all
• Maps SDK Version: com.mapbox.maps:android-ndk27:11.25.0

Observed behavior and steps to reproduce

I need to set a custom user agent on Mapbox tile requests. I have code that looks like this. Note that the user agent that is set via "User-Agent" is ignored; one must use the incorrect "user-agent" as the header name.

        HttpServiceFactory.setHttpServiceInterceptor(object : HttpServiceInterceptorInterface {
            override fun onRequest(
                request: HttpRequest,
                continuation: HttpServiceInterceptorRequestContinuation
            ) {
                // Set user agent on requests; some servers check this
                request.headers["User-Agent"] = NetworkUtils.USER_AGENT_STRING
                // TODO: Mapbox incorrectly uses the header in lowercase.  Remove when fixed in Mapbox.
                request.headers["user-agent"] = NetworkUtils.USER_AGENT_STRING
                continuation.run(HttpRequestOrResponse(request))
            }

This worked in previous versions of Mapbox but broke sometime in the last year or two.

Expected behavior

Here is the RFC that documents that the correct name of the header is "User-Agent" (capitalized).

https://httpwg.org/specs/rfc9110.html#field.user-agent

The iOS Mapbox library uses the correct "User-Agent".

[akirmse]

I see that in HTTP2, all header names must be transmitted in lowercase. So maybe this was just a silent library change that broke existing apps? It would be good to have the expected behavior documented, and consistency across Android and iOS versions of the library. Or this header map could be made case-insensitive so that existing apps continue to work.