.Net: Bug: .NET api-key header not sent - OpenAIChatCompletion not working with Azure AI Foundry deployments

Describe the bug
api-key header is not being sent when using the AddOpenAIChatCompletion Kernel extensions. Instead an Authorization: Bearer * header is being sent which does not work with Azure AI Foundry deployments - they require an api-key header.

To Reproduce
Steps to reproduce the behavior:

1. Register an OpenAI chat client:

            services.AddOpenAIChatCompletion(
                modelId: modelId,
                serviceId: modelId,
                openAIClient: new OpenAIClient(
                    credential: new ApiKeyCredential(
                        apiKey
                    ),
                    options: new OpenAIClientOptions
                    {
                        Endpoint = new Uri(endpoint)
                    }
                )
            );

2. Obtain it and send a request:

        var chatModel = _semanticKernel.GetRequiredService<IChatCompletionService>(chatModelInfo.ModelId);
        var response = await chatModel.GetChatMessageContentAsync(
                    chatHistory: _chatHistory,
                    kernel: _Kernel);

3. The request will fail with a 401 Unauthorized

Expected behavior
api-key header should be sent

Platform

• Language: C#
• Source: v. 1.3.6
• AI model: Phi-3-small-8k-instruct

Additional context
Obviously it can be worked around with a custom HTTP client that's sending the correct header, but this being a Microsoft-supported package it should integrate with Microsoft products seamlessly.

The URL https://.services.ai.azure.com/models is passed to the endpoint parameter.
From the official docs it would seem that this is supported out-of-the-box, but it's not. https://learn.microsoft.com/bg-bg/azure/ai-foundry/model-inference/concepts/endpoints?tabs=csharp#routing