Let not-found functions pass through FunctionInvokingChatClient

[jozkee]

FICC today creates a FunctionResultContent with result "Error: Requested function "{result.CallContent.Name}" not found".

extensions/src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs

Line 812 in 2fbb776

FunctionInvocationStatus.NotFound => $"Error: Requested function \"{result.CallContent.Name}\" not found.",

For handling approvals on the McpChatClient (#6492 (4)), we will need to modify FICC to allow FunctionCallContent to pass through if the function wasn't found.

This would be a breaking change.

cc @stephentoub

[stephentoub]

This would be a breaking change.

It'll be a functional change, but I think the current behavior is arguably a bug and it's unlikely folks are hitting this case.