fix(csharp): escape reserved keywords in enum value declarations

[yashhzd]

Summary

Fixes #31

Enum values using C# reserved keywords (e.g. event, fixed, virtual) produce invalid C# code that fails to compile. This PR applies the existing toCSharpIdentifier method to enum value names, which prefixes reserved keywords with _ — consistent with how field names are already handled.

When an enum value name is escaped, a [System.Runtime.Serialization.EnumMember(Value = "originalName")] attribute is added to preserve the original name during JSON serialization, matching the existing pattern used for the @AcceptedValue decorator.

Changes

• lib/codegen/fromcto/csharp/csharpvisitor.js: Modified visitEnumValueDeclaration to pass enum value names through toCSharpIdentifier and add EnumMember attribute when the name is escaped.
• test/codegen/fromcto/csharp/csharpvisitor.js: Added integration test with reserved keyword enum values (event, fixed, virtual) and unit tests for both reserved and non-reserved enum value names.

Example

Before (invalid C#):

enum Status {
    Active,
    event,   // compilation error — reserved keyword
    fixed,   // compilation error — reserved keyword
}

After (valid C#):

enum Status {
    Active,
    [System.Runtime.Serialization.EnumMember(Value = "event")]
    _event,
    [System.Runtime.Serialization.EnumMember(Value = "fixed")]
    _fixed,
}

Testing

All 569 tests pass (3 new tests added). No existing tests broken.

[Copilot]

Pull request overview

This PR fixes a critical compilation bug where C# reserved keywords used as enum values generate invalid C# code. The fix applies the existing toCSharpIdentifier method to escape reserved keywords with an underscore prefix and adds EnumMember attributes to preserve original names during JSON serialization.

Changes:

• Modified visitEnumValueDeclaration to escape reserved keywords in enum value names using toCSharpIdentifier
• Added EnumMember attribute when enum value names are transformed to preserve original serialization behavior
• Added comprehensive integration and unit tests covering reserved keywords in enum values

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib/codegen/fromcto/csharp/csharpvisitor.js	Modified visitEnumValueDeclaration to apply toCSharpIdentifier transformation and conditionally add EnumMember attribute for escaped enum values
test/codegen/fromcto/csharp/csharpvisitor.js	Added integration test with reserved keywords (event, fixed, virtual) and two unit tests verifying both reserved and non-reserved enum value handling

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