The validity of the authorization and issuance of the refunding bonds shall not be dependent on or affected in any way by proceedings taken for the improving of any enterprise for the refinancing and improving of which the refunding bonds are to be issued or by contracts made in connection with the improving of any such enterprise. Any resolution authorizing refunding bonds may provide that any such refunding bond may contain a recital that such refunding bond is issued pursuant to this chapter and any refunding bond containing such recital under authority of any such resolution shall be conclusively deemed to be valid and to have been issued in conformity with the provisions of this chapter.