Adds required() validation constraints to all the bookshelfModel's foreign keys, as defined in baseQuery.
function addConstraintsForForeignKeys (bookshelfModel, baseQuery) {
  if (typeof baseQuery === 'undefined') {
    return
  }
  
  _.forEach(baseQuery({params: {}, payload: {}}), function(v, k) {
    const value = bookshelfModel.prototype.schema[k]
    if (typeof value === 'undefined') {
      bookshelfModel.prototype.schema[k] = Joi.any().required()
    }
    else if (value.isJoi) {
      bookshelfModel.prototype.schema[k] = bookshelfModel.prototype.schema[k].required()
    }
  })
}