[BUG] [AI] [Projects] Custom Keys Auth failed for GetConnectionClient().GetConnectionAsync()

[glharper]

Library name and version

Azure.AI.Projects 1.0.0-beta.4

Describe the bug

Using the sample code in repro steps against a Custom Keys auth connection throws "System.ArgumentOutOfRangeException: Unknown AuthenticationType value. (Parameter 'value')
Actual value was CustomKeys."

Note that getting that Custom Auth connection in the python Projects SDK works correctly, and non-custom auth connections can be enumerated correctly in .NET Projects SDK.

Expected behavior

Custom Auth connection enumeration doesn't throw, connection response properly listed.

Actual behavior

Unhandled exception. System.ArgumentOutOfRangeException: Unknown AuthenticationType value. (Parameter 'value')
Actual value was CustomKeys.
at Azure.AI.Projects.AuthenticationTypeExtensions.ToAuthenticationType(String value)
at Azure.AI.Projects.UnknownInternalConnectionProperties.DeserializeUnknownInternalConnectionProperties(JsonElement element, ModelReaderWriterOptions options)
at Azure.AI.Projects.ConnectionProperties.DeserializeConnectionProperties(JsonElement element, ModelReaderWriterOptions options)
at Azure.AI.Projects.ConnectionResponse.DeserializeConnectionResponse(JsonElement element, ModelReaderWriterOptions options)
at Azure.AI.Projects.ConnectionResponse.FromResponse(Response response)
at Azure.AI.Projects.ConnectionsClient.GetConnectionAsync(String connectionName, CancellationToken cancellationToken)
at Program.Main(String[] args) in <PROJECT_PATH>\project_test\Program.cs:line 38
at Program.

(String[] args)

Reproduction Steps

run the following code:

        var connectionString = "project_connection_string";
        var modelName = "model"; //"gpt-4o-mini" for example

        var clientOptions = new AIProjectClientOptions();

        // Adding the custom headers policy
        clientOptions.AddPolicy(new CustomHeadersPolicy(), HttpPipelinePosition.PerCall);
        var projectClient = new AIProjectClient(connectionString, new AzureCliCredential(), clientOptions);

        ConnectionResponse sharepointConnection = await projectClient.GetConnectionsClient().GetConnectionAsync("custom_auth_key_connection_name");
        var connectionId = sharepointConnection.Id;

Environment

.NET SDK:
Version: 9.0.103
Commit: 96da45d427
Workload version: 9.0.100-manifests.ea610b94
MSBuild version: 17.12.24+90b52dda6

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19045
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\9.0.103\