dist/ember-json-api.js
function(record, json, relationship) {
        var attr = relationship.key;
        var belongsTo = record.belongsTo(attr);
        var type, key;

        if (isNone(belongsTo)) {
          return;
        }

        type = this.keyForSnapshot(belongsTo);
        key = this.keyForRelationship(attr);

        if (!json.links) {
          json.links = json.relationships || {};
        }
        json.links[key] = belongsToLink(key, type, get(belongsTo, 'id'));
      }
function(record, json, relationship) {
        var attr = relationship.key;
        var belongsTo = record.belongsTo(attr);
        var type, key;

        if (isNone(belongsTo)) {
          return;
        }

        type = this.keyForSnapshot(belongsTo);
        key = this.keyForRelationship(attr);

        if (!json.links) {
          json.links = json.relationships || {};
        }
        json.links[key] = belongsToLink(key, type, get(belongsTo, 'id'));
      }
function ( record , json , relationship ) { var attr = relationship . key ; var belongsTo = record . belongsTo ( attr ) ; var type , key ; if ( isNone ( belongsTo ) ) { return ; } type = this . keyForSnapshot ( belongsTo ) ; key = this . keyForRelationship ( attr ) ; if ( ! json . links ) { json . links = json . relationships || { } ; } json . links [ key ] = belongsToLink ( key , type , get ( belongsTo , 'id' ) ) ; }
Use "links" key, remove support for polymorphic type
Use links key remove support for polymorphic type