Changes to Create message

added the new optional request property model

added the new optional request property number_of_messages_to_include

added the new optional request property only_include_docs_used

removed the request property only_include_docs_used

added the new optional request property use_agentic_search

added the new optional request property rag_context

removed the request property model

removed the request property number_of_messages_to_include

removed the request property rag_context

removed the request property use_agentic_search