[Feature request] Field to specify user ID and session ID

It would be great if the web ui had a field to specify the user and session ID, perhaps next to the dropdown menu to choose the agent.
It would be very valuable: I have use cases where a custom tool performs an action using the user_id for example filtering RAG documents, or creating a ticket on a support platform. As of now, I can use my agent with an external frontend only, which specifies the `user_id` field in the REST API calls.