Allow custom relation path (http) - enable hasOne remoting access

[fabien]

Specify options: { path: 'plural-name' } to set custom relation paths, regardless of as:

// Relation path setting - final api: /users/1/public-photos
User.hasMany('Photo', { 
  as: 'publicPhotos', 
  scope: { where: { public: true } }, 
  options: { path: 'public-photos' }
});

See also: loopbackio/loopback-datasource-juggler#199