[Http][Kiota] Include Kiota API Client code generation as part of the Uno Kiota Extension

[kazo0]

Along with work from #2510

Currently, the generation of the kiota classes based on the openapi json/yml spec needs to be done manually before building the project.

See: https://learn.microsoft.com/en-us/openapi/kiota/using#client-generation

We need to find a way to incorporate this into the build process when using the Kiota Uno Extension.

Proposed API

I am imagining something like an IHostBuilder extension method called .UseKiota("PATH_TO_API_SPEC.json") or perhaps on a per client basis like:

hostBuilder.UseHttp((context, services) => services
	.AddKiotaClient("PATH_TO_API_SPEC.json")
	.AddKiotaClient("PATH_TO_A_DIFFERENT_API_SPEC.yml")
);

[dr1rrb]

IMO We should distinguish 2 cases:

1. The API is in the same solution of the client, i.e. "local"
2. The API is a "external"

Local API

In that case the API is evolving with the client, and we will need to re-generate the DTO pretty frequently. In that case we could a similar approach as described here https://nikiforovall.github.io/dotnet/aspnetcore/2024/03/24/kiota-guide-deep-dive.html#generate-openapi-specification-automatically

Basically when we compile the server we request generate the spec json file and we use it right away to run kiota gen and generate the code to be used by the client (directly in client folder).

For this we need to update Uno's new solution wizard to include an option for the server to use kiota or not.

• When not using kiota we should keep the current structure with a DTO project shared between the server and the client,
• When using kiota we should remove that project and include all tasks to run generation as described above.

External API

The API will most likely not change very often and kiota generator will have to be run only once. While it would be nice, having a generator for that is probably overkill.