message: Expand record-related interfaces.
diff: import { isObject, isNone } from './lib/objects';
  +import { Dict } from './lib/dict';
  export interface RecordIdentity {
  type: string;
  id: string;
  }
  +export interface RecordKey {
  + string;
  +}
  +
  +export interface RecordIdentifier {
  + string;
  +}
  +
  +export interface RecordAttribute {
  + any;
  +}
  +
  +export interface RecordHasOneRelationship {
  + data: null | RecordIdentifier;
  +}
  +
  +export interface RecordHasManyRelationship {
  + data: Dict<RecordIdentifier>;
  +}
  +
  +export type RecordRelationship = RecordHasOneRelationship | RecordHasManyRelationship;
  +
  export interface Record extends RecordIdentity {
  - keys?: Object; // TODO
  - attributes?: Object;
  - relationships?: Object; // TODO
  + keys?: Dict<RecordKey>;
  + attributes?: Dict<RecordAttribute>;
  + relationships?: Dict<RecordRelationship>;
  }
  export function serializeRecordIdentity(identity: RecordIdentity): string {
  