[BUG] [csharp-client] Query parameters do not get escaped

Created by: HerrNiklasRaab

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Query parameters do not get escaped, when using HttpClient (not Restsharp). When I pass a query parameter, let's say "2021-07-23T22:55:43.3041130+02:00" this gets added to the request URL like it is. Because the + is interpreted as whitespace the server receives this value "2021-07-23T22:55:43.3041130 02:00". See the + is replaced by the whitespace. Shouldn't the client that was generated make sure that all parameters are escaped? In this case the + should be replaced with %2B, right?

According to the spect this is the expected behavior.

openapi-generator version

stable 5.2.0

OpenAPI declaration file content or url

In my case I used a query parameter with DateTimeOffset, but a query parameter with string would work as well.

Generation Details

targetFramework: net5.0 packageName: Brokkoli.Api.Client sourceFolder: "" useDateTimeOffset: true library: httpclient

If this is actually a bug, I'm willing to sponsor work on this issue to the tune of $50. cc @wing328