A key-value fact associated with a user, persisted across conversations.
Facts are simple string pairs — the key identifies what is known, the value
holds the information. Save is upsert: writing to the same {user_id, key}
silently overwrites the previous value.
Summary
Types
@type t() :: %PhoenixAI.Store.LongTermMemory.Fact{ id: String.t() | nil, inserted_at: DateTime.t() | nil, key: String.t(), updated_at: DateTime.t() | nil, user_id: String.t(), value: String.t() }