[BUG][csharp-netcore] Ignoring `EnumMember.Value` when converting an enum query parameter to string

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

The EnumMember.Value (e.g. [EnumMember(Value = "opened")] Opened = 2) is not considered during enum to string conversion.

• False conversion (current): State = State.Opened is converted to Opened
• Expected conversion: State = State.Opened is converted to opened

openapi-generator version

5.2.0

OpenAPI declaration file content or url

type: string
enum:
  - all
  - opened 
  - closed

Generation Details

openapi-generator-cli generate -g csharp-netcore --additional-properties=targetFramework=net5.0 --additional-properties=packageName=My.Namespace -o out -i PATH\TO\openapi.yaml

The generated code looks like the following:

[JsonConverter(typeof (StringEnumConverter))]
public enum State
{
  [EnumMember(Value = "all")] All = 1,
  [EnumMember(Value = "opened")] Opened = 2,
  [EnumMember(Value = "closed")] Closed = 3,
}

Steps to reproduce

• Just generate the client and perform a query with an enum as a query parameter.
• The query parameter will have a capitalized first letter even if EnumMember.Value = "opened"

Related issues/PRs

Suggest a fix

Start with the csharp-netcore generator using the reported openapi-generator-cli command and inspect how generated enum query parameters are converted to strings. Reproduce the request with the generated State enum and verify that the query value uses EnumMember.Value, such as "opened", rather than the C# member name "Opened".