Update test/documentation for role/user_name change

[billytrend-cohere]

Supports changes to role/user_name interface in chat_history when that is merged.

Fixes PTS-4996

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}