code: function compile_constraints(request, constraints) {
    const Constraints = require("./constraints")
    
    // Exit if there aren't any constraints.
    if (!constraints)
      return {}
  
    return new Constraints()
      .set_source(request)
      .set_rules(constraints)
      .compile()
      .results
  }
docs: Compile any constraints and return an object.
  @param  {Hapi.Request} request to the server.
  @param  {Waterline.Collection} collection to get constraints from.
  @return {Object} compiled constraints.