Support is read from model.profile (see
https://docs.langchain.com/oss/javascript/langchain/models#model-profiles).
Place this middleware last in the agent's middleware list, so that if
some other middleware changes request.model, this one sees the model
that will actually receive the request.
createUnsupportedContentMiddleware(
): AgentMiddleware<undefined, undefined, unknown, readonly ClientTool | ServerTool[], readonly []>