Unable to start a repeater

[derevnjuk]

SecTester crashes while starting a new repeater on https://app.neuralegion.com/ due to an empty response body on POST /api/v1/repeaters

Precondition:

1. Create a Bright API key (https://docs.brightsec.com/docs/manage-your-personal-account#manage-your-personal-api-keys-authentication-tokens) with all available scopes.
2. Put created API key under BRIGHT_TOKEN env variable.

Steps to reproduce:

1. Configure SecTester using the XUnit test framework as follows (https://github.com/NeuraLegion/sectester-net/tree/master/src/SecTester.Runner#setup):

using SecTester.Runner;
using SecTester.Scan;
using SecTester.Scan.Models;

public class Tests : IAsyncLifetime
{
  private const string Hostname = "app.brightsec.com";
  private readonly Configuration _config = new(Hostname, logLevel: LogLevel.Trace);

  private readonly SecRunner _runner;
  private readonly ScanSettingsBuilder _settings = new ScanSettingsBuilder()
    .WithTests(new List<TestType> { TestType.RetireJs });

  public async Task InitializeAsync()
  { 
    _runner = await SecRunner.Create(_config);
    await _runner.Init();
  }

  public async Task DisposeAsync()
  {
    await _runner.DisposeAsync();
    GC.SuppressFinalize(this);
  }
}

2. Implement a test against any target:

// ...

public class Tests : IAsyncLifetime
{
  // ...
   [Fact]
  public async Task ShouldNotHaveJsVulnerability()
  {
    var target = new Target("https://qa.brokencrystals.com/vendor/fullcalendar-3.10.0/lib/moment.min.js")
      .WithHeaders(new Dictionary<string, IEnumerable<string>>
      {
        { "Accept-Encoding", new[] { "identity" } }
      });

    await _runner
      .CreateScan(_settings)
      .Threshold(Severity.Medium)
      .Timeout(TimeSpan.FromMinutes(50))
      .Run(target);
  }
}

3. Run the test by issuing the following command:

$ dotnet test -c Debug --nologo --logger "console;verbosity=detailed" --filter "DisplayName~ShouldNotHaveJsVulnerability"

Expected result: scan has been started without any issues.

Actual result: unable to start a repeater, tests crashes with the following stack trace:

[xUnit.net](http://xunit.net/) 00:00:03.12]     App.SecurityTests.AppTests.Get_Users_ShouldNotHaveSqli [FAIL]
  Failed App.SecurityTests.AppTests.Post_Users_ShouldNotHaveXss [1 ms]
  Error Message:
   System.Text.Json.JsonException : The input does not contain any JSON tokens. Expected the input to start with a valid JSON token, when isFinalBlock is true. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
---- System.Text.Json.JsonReaderException : The input does not contain any JSON tokens. Expected the input to start with a valid JSON token, when isFinalBlock is true. LineNumber: 0 | BytePositionInLine: 0.
  Stack Trace:
     at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCoreAsObject(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadFromSpan[TValue](ReadOnlySpan`1 utf8Json, JsonTypeInfo jsonTypeInfo, Nullable`1 actualByteCount)
   at System.Text.Json.JsonSerializer.ReadFromSpan[TValue](ReadOnlySpan`1 json, JsonTypeInfo jsonTypeInfo)
   at System.Text.Json.JsonSerializer.Deserialize(String json, Type returnType, JsonSerializerOptions options)
   at SecTester.Bus.Dispatchers.MessageSerializer.Deserialize(String data, Type type) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Bus/Dispatchers/MessageSerializer.cs:line 26
   at SecTester.Bus.Dispatchers.MessageSerializer.Deserialize[T](String data) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Bus/Dispatchers/MessageSerializer.cs:line 24
   at SecTester.Bus.Dispatchers.HttpCommandDispatcher.ParserResponse[TResult](HttpResponseMessage res) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Bus/Dispatchers/HttpCommandDispatcher.cs:line 59
   at SecTester.Bus.Dispatchers.HttpCommandDispatcher.Execute[TResult](Command`1 message) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Bus/Dispatchers/HttpCommandDispatcher.cs:line 46
   at SecTester.Repeater.Api.DefaultRepeaters.CreateRepeater(String name, String description) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Repeater/Api/DefaultRepeaters.cs:line 20
   at SecTester.Repeater.DefaultRepeaterFactory.CreateRepeater(RepeaterOptions options) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Repeater/DefaultRepeaterFactory.cs:line 36
   at SecTester.Runner.SecRunner.Init(RepeaterOptions options, CancellationToken cancellationToken) in /home/runner/work/sectester-net/sectester-net/src/SecTester.Runner/SecRunner.cs:line 74
   at App.SecurityTests.AppTests.InitializeAsync() in /home/git-bob/sectestering2/sectester-net-demo/test/App.SecurityTests/AppTests.cs:line 20