The role of the entity that is creating the message. Currently only user is
supported.
optional
file_ids: Array<string>
A list of File IDs that
the message should use. There can be a maximum of 10 files attached to a
message. Useful for tools like retrieval and code_interpreter that can
access and use files.
optional
metadata: unknown | null
Set of 16 key-value pairs that can be attached to an object. This can be useful
for storing additional information about the object in a structured format. Keys
can be a maximum of 64 characters long and values can be a maxium of 512
characters long.