adds support for overlays

[kilifu]

• add overlays option
• caching overlay seams ok
• cleanup
• ad d BinkyLabs.OpenApi.Overlays

[Copilot]

Pull Request Overview

Adds support for processing overlay definitions during client and plugin generation, including command‐line options, server RPC methods, and document application logic.

• Introduced an overlays option/property throughout TypeScript and C# generation interfaces
• Extended Kiota CLI commands and handlers to accept and propagate overlays
• Enhanced OpenApiDocumentDownloadService to read, apply, and merge overlay documents, plus added unit tests

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
vscode/packages/npm-package/types.ts	Added overlays to generation configuration types
vscode/packages/npm-package/lib/generatePlugin.ts	Propagate overlays into plugin generation API and docs
vscode/packages/npm-package/lib/generateClient.ts	Propagate overlays into client generation API and docs
tests/Kiota.Builder.Tests/OpenApiDocumentDownloadServiceTests.cs	Added tests for overlay handling in document downloader
src/kiota/Rpc/Server.cs	Updated RPC GenerateAsync methods to include overlays parameter
src/kiota/Rpc/IServer.cs	Updated interface signatures to include overlays
src/kiota/KiotaPluginCommands.cs	Added --overlays option for plugin commands
src/kiota/KiotaHost.cs	Added --overlays option for generate command
src/kiota/KiotaClientCommands.cs	Added --overlays option for client commands
src/kiota/Handlers/Plugin/EditHandler.cs	Wired up OverlaysOption in plugin edit handler
src/kiota/Handlers/Plugin/AddHandler.cs	Wired up OverlaysOption in plugin add handler
src/kiota/Handlers/KiotaGenerateCommandHandler.cs	Wired up OverlaysOption for generate handler
src/kiota/Handlers/Client/EditHandler.cs	Wired up OverlaysOption in client edit handler
src/kiota/Handlers/Client/AddHandler.cs	Wired up OverlaysOption in client add handler
src/Kiota.Builder/OpenApiDocumentDownloadService.cs	Implemented overlay document loading and application
src/Kiota.Builder/Lock/KiotaLock.cs	Added Overlays to lock file serialization
src/Kiota.Builder/Kiota.Builder.csproj	Added NuGet package reference for overlays support
src/Kiota.Builder/Configuration/GenerationConfiguration.cs	Added Overlays property and included in clone

Comments suppressed due to low confidence (2)

vscode/packages/npm-package/lib/generateClient.ts:55

• Update the docstring for overlays to accurately describe that it is a list of overlay file paths or URLs to apply, e.g., 'List of overlay definitions to apply during client generation.'

 * @param {string[]} [clientGenerationOptions.overlays] - Whether the generated client uses overlays.

src/kiota/Rpc/Server.cs:180

• [nitpick] Use the local configuration variable consistently instead of Configuration.Generation to keep assignments uniform within this method.

            configuration.Overlays = new(overlays);

[Copilot]

Ensure the target directory exists before writing the overlay file and use Path.Combine(workingDirectory, "overlays.yaml") for correct filepath; consider calling Directory.CreateDirectory first.

Suggested change

	var overlaysPath = Path.GetRandomFileName() + "overlays.yaml";
	var workingDirectory = Path.Combine(Path.GetTempPath(), "Overlays");
	Directory.CreateDirectory(workingDirectory);
	var overlaysPath = Path.Combine(workingDirectory, "overlays.yaml");

[Copilot]

This check uses Directory.Exists on a file path. Switch to File.Exists(overlaysPath) and delete with File.Delete to clean up the overlay file correctly.

Suggested change

	if (Directory.Exists(overlaysPath))
	Directory.Delete(overlaysPath, true);
	if (File.Exists(overlaysPath))
	File.Delete(overlaysPath);

[Copilot]

The clone method assigns the same Overlays instance rather than copying it. Change to Overlays = Overlays.ToHashSet(StringComparer.OrdinalIgnoreCase) to avoid shared mutable state.

Suggested change

	Overlays = Overlays
	Overlays = Overlays?.ToHashSet(StringComparer.OrdinalIgnoreCase)

[Copilot]

[nitpick] Either implement support for multiple overlays or remove/update this TODO with a clearer next step to avoid stale comments.

Suggested change

	// TODO : handle multiple Overlays
	var overlay = config.Overlays.First();

[baywet]

Why the difference in implementation between the two methods