The rolling, incrementally-generated summary of a thread.
@type t() :: %Zep.Schemas.ThreadSummary{ created_at: String.t() | nil, last_summarized_at: String.t() | nil, last_summarized_episode_valid_at: String.t() | nil, summary: String.t() | nil, thread_id: String.t() | nil, uuid: String.t() | nil }