Use HTTP 1.1 by default

Description

Configures the default HttpClient to use HTTP 1.1 by default.

There are issues observed using HTTP 2 with FGA, as observed in #126 and failures related to receiving GOAWAY frames.

This change updates the default configuration to use HTTP 1.1.

It also includes a new constructor for ApiClient, to enable easier configuration for a custom HttpClient. If customers wish to use HTTP 2, with this change they can configure the SDK like the following:

// HttpClient.Builder configured for HTTP 2.0
HttpClient.Builder httpBuilder = HttpClient.newBuilder().version(HttpClient.Version.HTTP_2);

final var apiClient = new ApiClient(httpBuilder);

var fgaClient = new OpenFgaClient(configuration, apiClient);

References

#126

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected