Refactor HttpClient to use IHttpClientFactory to prevent socket exhaustion

[Copilot]

McpToolServerConfigurationService was creating new HttpClient instances per request via RuntimeUtility.GetDefaultHttpClient(), which prevents connection pooling and can cause socket exhaustion under load.

Changes

• RuntimeUtility.GetDefaultHttpClient: Updated to accept an optional IHttpClientFactory parameter. When provided, uses the factory to create HttpClient instances; otherwise falls back to direct instantiation for backward compatibility.
• McpToolServerConfigurationService: Inject IHttpClientFactory and pass it to RuntimeUtility.GetDefaultHttpClient() in SendChatHistoryAsync and GetMCPServerFromToolingGatewayAsync
• ServiceCollectionExtensions: Register IHttpClientFactory via services.AddHttpClient()
• Tests: Mock IHttpClientFactory in test setup

Example

Before:

using var httpClient = RuntimeUtility.GetDefaultHttpClient(userAgentConfiguration);

After:

var httpClient = RuntimeUtility.GetDefaultHttpClient(httpClientFactory: this._httpClientFactory, userAgentConfiguration: userAgentConfiguration);

This approach centralizes HttpClient configuration in RuntimeUtility.GetDefaultHttpClient while leveraging IHttpClientFactory for connection pooling. User-Agent configuration and other default behaviors are consistently applied. HttpClient instances from the factory are not disposed—the factory manages their lifecycle and connection pooling.

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[pontemonti]

@copilot - Make sure that RuntimeUtility.GetDefaultHttpClient is still used - it will have to retrieve the client instance. We want the user agent header (and any other default behavior we add) to always be included, and the current implementation makes that difficult.

[Copilot]

Updated RuntimeUtility.GetDefaultHttpClient to accept IHttpClientFactory as an optional first parameter. The service now calls this method with the injected factory, centralizing the User-Agent header configuration and any other default behaviors.

Changes in commits:

• fb9424c: Updated GetDefaultHttpClient signature and service usage
• 737948c: Cleaned up unnecessary using statement