Add --framework flag to minimize c# preprocessor directives

[ssnseawolf]

Is your feature request related to a problem? Please describe the problem.

Kiota generates code with C# preprocessor directives based on target framework. This code is larger than necessary when the target framework is known.

Consider the following generated code from Microsoft Graph that requires #nullable:

#if NETSTANDARD2_1_OR_GREATER || NETCOREAPP3_1_OR_GREATER
#nullable enable
        public string? AgeGroup
        {
            get { return BackingStore?.Get<string?>("ageGroup"); }
            set { BackingStore?.Set("ageGroup", value); }
        }
#nullable restore
#else
        public string AgeGroup
        {
            get { return BackingStore?.Get<string>("ageGroup"); }
            set { BackingStore?.Set("ageGroup", value); }
        }
#endif

Client library/SDK language

Csharp

Describe the solution you'd like

The above preprocessor directive may be eliminated with an optional Kiota CLI --framework argument, mimicking the dotnet build --framework argument.

For example:
kiota generate -o x.yaml -l csharp --framework net8.0

When --framework argument is missing: Preprocessor directives are generated as they currently are. The code above is generated as-is.

When --framework argument is present: No preprocessor directives are generated since the target framework is known. For example, in the example above, if the --framework net8.0 is passed, the result would instead be:

#nullable enable
        public string? AgeGroup
        {
            get { return BackingStore?.Get<string?>("ageGroup"); }
            set { BackingStore?.Set("ageGroup", value); }
        }
#nullable restore

Additional context

Allowing the user to optionally enter a target framework reduces the amount of generated code and improves readability. Users who use Kiota-generated code across a range of .NET target environments and do not pass the proposed --framework argument would see no change in generated code.

[baywet]

Hi @ssnseawolf
Thank you for using kiota and for reaching out.
This is something we're unlikely to add or accept as a pull request.
Here are discussions that should provide additional background.
#3944
#3911
Let us know if you have any additional comments or questions.

[ssnseawolf]

Appreciate the detailed discussion and justification in the linked issues. Kiota's good stuff - keep it up.