fix: update OpenAPI Generator to 6.1.0 for dotnet to support Blazor WebAssembly

[sbward]

Related Issue or Design Document

#299

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact [email protected]) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

.NET Blazor WebAssembly projects must use HttpClient for web requests, however Ory SDK is using a version of OpenAPI Generator (5.4.1) which generates code using RestSharp 106.13.0, which is does not use HttpClient.

Using RestSharp 107+ fixes the issue, and OpenAPI Generator adopts a recent enough version of RestSharp (108.0.3) in version 6.1.0.

RestSharp 107 was a breaking change which drops support for .NET 4.5 (which is no longer supported by Microsoft). For more details see: https://github.com/restsharp/RestSharp/releases/tag/107.0.0

[aeneasr]

Upgraded to 7.4.0 on master :)