Support for Kiota

[bkoelman]

Add support for using Kiota to generate a C# client, aside from the existing NSwag support.

• Rename JsonApiDotNetCore.OpenApi.Client to JsonApiDotNetCore.OpenApi.Client.NSwag
• Create sample
  • Consider switching to Worker Service project template, so we can use IHttpClientFactory from the IoC container
  • Investigate how to re-generate the client code during build, see Microsoft.OpenApi.Kiota.ApiDescription.Client microsoft/kiota#3005
• Create tests
  • Make server-side tests write their swagger.g.json elsewhere during testrun, not directly into the client project(s)
• Update documentation

An initial experiment is available at https://github.com/json-api-dotnet/JsonApiDotNetCore/tree/openapi-tryout-kiota.

[bkoelman]

Related: should set OutputPath for NSwag in the example project and/or LegacyOpenApiIntegration. This makes it easy to spot how the generated client changes when trying out different switches or updating to a newer version.

[bkoelman]

Should include a test that verifies public IDictionary<string, object> AdditionalData { get; set; } is only generated for meta properties.

[bkoelman]

Should clean up references to Swashbuckle* packages.