OptionalparentResource name of the containing session store, in the form
session-stores/{session_store_id}.
OptionalsessionThe session to create. actor_id is required. A session with parent_session_id is a child and
must use its parent's actor_id. Independent forks are created only through ForkSession.
OptionalsessionOptional caller-selected session ID. The service generates a UUID when this field is omitted.
The ID must be unique; a collision returns ALREADY_EXISTS.
Request to create a session.