Add OpenCLI Specification Option for `System.CommandLine`

[Flash0ver]

Summary

Add System.CommandLine Option for OpenCLI Specification via --open-cli or --opencli.

Remarks

• based on: Initial scaffolding for CLI introspection #2

An OpenCLI Description is a single JSON or YAML document that conforms to the OpenCLI Specification.
_{see: https://opencli.org/#opencli-description}

The OpenCLI Specification is built-in to Spectre.Console.Cli through exe cli opencli and exe --help-dump-opencli.
See: https://spectreconsole.net/cli/reference/built-in-command-behaviors/#opencli-command

Features

• Add a public API that adds an Option<bool> to System.CommandLine applications
  • Option<bool> should not be recursive, to allow to JSONify only the RootCommand
  • Option<bool> should be hidden, to not show in the help output
• Might accept optional JSON-Serializer options
• Add a parameter for the OpenCLI Version as enum or struct
  • see: https://opencli.org/#versions
• Mark OpenCLI-Version-related APIs [Experimental]
  • the OpenCLI Specification is currently a draft/proposal in Version 0.1
  • there are still breaking changes to the draft/proposal of Version 0.1
  • documentation should mention the date of the current revision in use
  • see changelog: https://opencli.org/
• Should be Trim-friendly and AOT-compatible, or have an overload that is
• Use System.Text.Json to output the JSON representation
  • target frameworks without built-in support as part of the shared framework should use the System.Text.Json NuGet package
• Use StringSyntaxAttribute.Json for testing
• Add Benchmarks for relevant public members
• Set appropriate <TargetFrameworks> for the Library
  • use multi-targeting for the Test project
• Ensure to be callable/invocable from C#, F#, and Visual Basic

Example

See: https://opencli.org/examples

See also

• System.CommandLine repository: https://github.com/dotnet/command-line-api
• System.CommandLine documentation: https://learn.microsoft.com/dotnet/standard/commandline/
• System.Text.Json documentation: https://learn.microsoft.com/dotnet/standard/serialization/system-text-json/overview
• Trimming: https://learn.microsoft.com/dotnet/core/deploying/trimming/trim-self-contained
• Native AOT: https://learn.microsoft.com/dotnet/core/deploying/native-aot
• OpenCLI repository: https://github.com/spectreconsole/open-cli
• Spectre.Console.Cli repository: https://github.com/spectreconsole/spectre.console.cli

[Flash0ver]

TODO

• default Option name/alias
  • --open-cli
  • --opencli
• Open issue for features of the OpenCLI Specification that are missing from System.CommandLine
  • Issue