Use invariant culture for uppercase & lowercase

[zelakus]

Objective

Fixing invalid characters in web request headers on Turkish OS display language.

InvalidOperationException: Header value contains invalid characters
UnityEngine.Networking.UnityWebRequest.SetRequestHeader (System.String name, System.String value) (at <63fb9d7bd92242a7b4218da88657af33>:0)
Xsolla.Core.WebRequestHelper.AttachHeadersToRequest (UnityEngine.Networking.UnityWebRequest webRequest, System.Collections.Generic.List`1[T] requestHeaders) (at Assets/Xsolla/Core/WebRequests/WebRequestHelper.cs:117)
Xsolla.Core.WebRequestHelper.AttachHeadersToPostRequest (UnityEngine.Networking.UnityWebRequest webRequest, System.Collections.Generic.List`1[T] requestHeaders, System.Boolean withContentType) (at Assets/Xsolla/Core/WebRequests/WebRequestHelper.POST.cs:285)
Xsolla.Core.WebRequestHelper.PreparePostWebRequest (System.String url, System.Object jsonObject, System.Collections.Generic.List`1[T] requestHeaders) (at Assets/Xsolla/Core/WebRequests/WebRequestHelper.POST.cs:247)
Xsolla.Core.WebRequestHelper+<PostRequestCor>d__62`1[T].MoveNext () (at Assets/Xsolla/Core/WebRequests/WebRequestHelper.POST.cs:194)
UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) (at <56073df97ede4f769c2cc45d546d986d>:0)
UnityEngine.MonoBehaviour:StartCoroutine(IEnumerator)
Xsolla.Core.WebRequestHelper:PostRequest(SdkType, String, SignInRequest, Action`1, Action`1, ErrorGroup) (at Assets/Xsolla/Core/WebRequests/WebRequestHelper.POST.cs:34)
Xsolla.Auth.XsollaAuth:SignIn(String, String, Action, Action`1, String) (at Assets/Xsolla/Auth/XsollaAuth.cs:110)

In this example stack trace was caused by the classic auth, but anything using Xsolla.Core.WebRequestHelper.GetUnityParameters has the same issue.

Cause

Xsolla Analytics is providing uppercase headers using OS Locale, turning X-BUILD-PLATFORM header's StandaloneWindows64 into STANDALONEWİNDOWS64 when display language of the OS is Turkish. As this uppercase İ is not a valid English character, the above exception was thrown.

Resolution

Turning upper and lower options into Invariant Culture fixed the issue.