[feature request] add 'role' field to BaseMessage to implement RBAC reasoning in LLM

BaseMessage has already fields the LLM ca see: name and author. But no role field is visible to LLM. right now if I need to implement some RBAC reasoning i must include role tag prefix ahead the message. Or I must use some dynamic propt workaround. Much more easier would be to include user/role as standard field in the message so that I can tall the LLM in the prompt that some particular action or response can be done only for specific roles.