Add delegate for HttpClient override

[AnPucel]

Description

This allows users to bring their own HttpClient instead of HttpClientHandler. This gives them more control over managing the lifecycle of the HttpClient if they choose, which is notoriously difficult in .Net. It also aligns with the recommended factory pattern of creating HttpClients recommended here

        public static HttpClient HttpClientProvider(HttpClientHandler handler)
        {
            return new HttpClient(handler);
        }

        VaultConfiguration config = new VaultConfiguration("http://127.0.0.1:8200", httpClientProvider: HttpClientProvider);

If you set the timeout when configuring VaultClient that will take precedent over any timeout configured in your provided HttpClient

Resolves # VAULT-9887

How has this been tested?

Tested locally with a generic HttpClient and preconfigured with some random settings.

[dhuckins]

what is Func here? shouldn't this be HttpClient?
(sorry if dumb question, looks weird from a non-c# perspective)

I saw IHttpClientFactory above, shouldn't it take that as the param type?

[AnPucel]

So, this is kind of weird. But because the VaultClient needs to configure the HttpClientHandler (for TLS among other things), which the HttpClient is dependent on we have to allow users to pass a delegate (i.e. Func) to new up their own HttpClient with our pre-configured client handler.

[AnPucel]

I was debating whether to allow just to pass their own HttpClient object, like you're suggesting, but if they wanted to utilize the TLS, then they'd have to preconfigure it, which may be annoying.

It could be that we offer both options.

[averche]

In the Go version, we allow you to provide HTTPClient directly but then override the TLS options (if configured). Not sure if this is something doable here.

[vxkc]

Does this make sense in the context of IHttpClientFactory, as the factory manages the HttpClientHandler instances?

[dhuckins]

bad link?

[AnPucel]

oh whooops