code: function allowModelScope (args) {
      // start new audit
      this.newAudit(args, 'modelScope')
      // check any scope
      args.scope = 'any'
      // check access
      var allow = this.allowModel(args)
      // access to any is allowed
      if (allow) {
          return this.audit.setScope('any')
      }
      // check own scope
      args.scope = 'own'
      // check access
      var allow = this.allowModel(args)
      // return own if allowed or undefined if denied
      return this.audit.setScope(allow ? 'own' : undefined)
  }
docs: @function allowModelScope
  
  get the scope allowed for a model action. this will be either any, own,
  or undefined if no scope is allowed.
  
  scope is determined by calling allowModel first with a scope of any and if
  that returns false then with a scope of all.
  
  @param {object} args
  @param {string} args.accessId
  @param {string} args.action
  @param {string} args.model
  @param {string} args.scope
  @param {object} args.session
  @param {array} args.states
  
  @returns {string|undefined}