message: fix(types): mark id, userId as optional in ThreadMember
diff: export interface ThreadMember {
  /** The id of the thread */
  - id: string;
  + id?: string;
  /** The id of the user */
  - userId: string;
  + userId?: string;
  /** The time the current user last joined the thread */
  joinTimestamp: string;
  /** Any user-thread settings, currently only used for notifications */
  