Add IPApiLite to support Lite API

[silvanocerza]

Similar approach to other libraries.

I had to update a System.Text.Json because of this security advisory.

On a side note we should probably also update the version of DotNet used for the library as is quite old.

[linear]

ENG-288 Add Lite API support to `ipinfo/csharp`

[silvanocerza]

I couldn't test this properly on my Mac as I had several issues trying to run tests.
I though CI would run those but I notice just now that they run only for releases so I took the liberty to add a new one. It will run on PRs and pushes to main.

[silvanocerza]

We need to update the token secret.

[max-ipinfo]

We need to update the token secret.

fixed

[max-ipinfo]

@silvanocerza I re-ran the tests and getting this error:

Run dotnet test
  Determining projects to restore...
  All projects are up-to-date for restore.
  IPinfo -> /home/runner/work/csharp/csharp/src/IPinfo/bin/Debug/netstandard2.0/IPinfo.dll
  IPinfo.Tests -> /home/runner/work/csharp/csharp/IPinfo.Tests/bin/Debug/net6.0/IPinfo.Tests.dll
Test run for /home/runner/work/csharp/csharp/IPinfo.Tests/bin/Debug/net6.0/IPinfo.Tests.dll (.NETCoreApp,Version=v6.0)
Microsoft (R) Test Execution Command Line Tool Version 1[7](https://github.com/ipinfo/csharp/actions/runs/16149797539/job/45732337990#step:6:8).3.3 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
[xUnit.net 00:00:00.90]     IPinfo.Tests.IPApiLiteTest.TestGetDetails [FAIL]
  Failed IPinfo.Tests.IPApiLiteTest.TestGetDetails [29 ms]
[xUnit.net 00:00:00.94]     IPinfo.Tests.IPApiLiteTest.TestGetDetailsIPV6 [FAIL]
  Error Message:
   System.NullReferenceException : Object reference not set to an instance of an object.
  Stack Trace:
     at IPinfo.Tests.IPApiLiteTest.TestGetDetails() in /home/runner/work/csharp/csharp/IPinfo.Tests/IPApiLiteTest.cs:line 21
[xUnit.net 00:00:00.97]     IPinfo.Tests.IPApiLiteTest.TestGetDetailsCurrentIP [FAIL]
  Failed IPinfo.Tests.IPApiLiteTest.TestGetDetailsIPV6 [31 ms]
  Error Message:
   System.NullReferenceException : Object reference not set to an instance of an object.
  Stack Trace:
     at IPinfo.Tests.IPApiLiteTest.TestGetDetailsIPV6() in /home/runner/work/csharp/csharp/IPinfo.Tests/IPApiLiteTest.cs:line 52
  Failed IPinfo.Tests.IPApiLiteTest.TestGetDetailsCurrentIP [39 ms]
  Error Message:
   IPinfo.Exceptions.RequestFailedGeneralException :  StatusCode = 404,
Body = {
  "error": "Endpoint not found. Did you mean /lite/me or /lite/[8](https://github.com/ipinfo/csharp/actions/runs/16149797539/job/45732337990#step:6:9).8.8.8?"
}
---- System.Net.Http.HttpRequestException : Response status code does not indicate success: 404 (Not Found).
  Stack Trace:
     at IPinfo.Utilities.ApiHelper.RunTaskSynchronously(Task t) in /home/runner/work/csharp/csharp/src/IPinfo/Utilities/ApiHelper.cs:line 27
   at IPinfo.Apis.IPApiLite.GetDetails(String ipAddress) in /home/runner/work/csharp/csharp/src/IPinfo/Apis/IPApiLite.cs:line 53
   at IPinfo.Tests.IPApiLiteTest.TestGetDetailsCurrentIP() in /home/runner/work/csharp/csharp/IPinfo.Tests/IPApiLiteTest.cs:line 80
----- Inner Stack Trace -----
   at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()
   at IPinfo.Apis.BaseApi.ValidateResponse(HttpContext context) in /home/runner/work/csharp/csharp/src/IPinfo/Apis/BaseApi.cs:line [9](https://github.com/ipinfo/csharp/actions/runs/16149797539/job/45732337990#step:6:10)3

[silvanocerza]

@max-ipinfo tests are green. 👍

On a side note we should probably make it possible to build the project locally without the need of a Strong Name Keypair, it will ease development quite a bit.