.Net: Issue 11562 (add plugin description)

[AleRoe]

Motivation and Context

The current ApiManifestKernelExtensions implementations (ImportPluginFromApiManifestAsync and CreatePluginFromApiManifestAsync) in Microsoft.SemanticKernel.Plugins.OpenApi.Extensions lack the capability to provide a description for the newly created KernelPlugin. Plugins should have a description to provide adequate context to the LLM regarding their purpose and use.

Ideally, the description is derived from the ApiManifestDocument, but the current Microsoft.OpenApi.ApiManifest.ApiManifestDocument implementation does not support a Description property.

This PR addresses issue #11562

Description

To get around this limitation, I've modified the CreatePluginFromApiManifestAsync implementation to accept a description parameter which is passed to the KernelPluginFactory.CreateFromFunctions() call and added two new method signatures to ensure backwards compatibility.
I've also added a new testclass (ApiManifestKernelExtensionsTests.cs) and apimanifest.json sample (which was missing so far) in SemanticKernel.Functions.UnitTests.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[AleRoe]

@microsoft-github-policy-service agree