The response is from an [entry prompt][google.cloud.dialogflow.cx.v3.Page.entry_fulfillment] in the page.
PARAMETER_PROMPT
The response is from [form-filling prompt][google.cloud.dialogflow.cx.v3.Form.Parameter.fill_behavior] in the page.
HANDLER_PROMPT
The response is from a [transition route][google.cloud.dialogflow.cx.v3.TransitionRoute] or an `event handler][EventHandler]` in the page or flow or transition route group.