Support injection of HttpClient instances

[martincostello]

The Connection class should be extensible enough to allow for interoperability with the HttpClientFactory in .NET Core 2.1.

This would allow users to use the out-of-the-box GraphQL client in their applications easily while applying cross-cutting concerns like retries, handler pooling, centralised configurability etc. without having to implement IConnection themselves to remove the HttpClient instance created privately per Connection instance.

[StanleyGoldman]

That is a very good suggestion.

[grokys]

Would an additional ctor implemented like this be sufficient?

public Connection(HttpClient client, Uri uri, ICredentialStore credentialStore)
{
    Uri = uri;
    CredentialStore = credentialStore;
    HttpClient = client;
}

[martincostello]

Maybe also one where the Uri isn’t required, given that I guess that exists just for Enterprise? The code would also need to add the UserAgent if not already present, or would you just leave that completely up to the integrator?

Happy to submit a PR if there’s a rough approach agreed.

[StanleyGoldman]

We are pretty interactive...
If you start me off with a unit test that shows us what you are thinking...
I can either take over or point you in the right directions to finish.

[martincostello]

Cool, I'll give that a whirl when I get next a spare hour or so.

[martincostello]

Have opened #131 with some very basic changes to Connection with a test showing the sort of things that can be achieved by supporting HttpClient injection.

[martincostello]

I guess this is closed now #131 is merged? 😺

[StanleyGoldman]

Yup.