Every sewer district and every water district previously created shall be reclassified and shall become a water-sewer district, and shall be known as the ". . . . . Water-Sewer District," or "Water-Sewer District No. . . . ." or shall continue to be known as a "sewer district" or a "water district," with the existing name or number inserted, as appropriate. As used in this title, "district" means a water-sewer district, a sewer district, or a water district. All debts, contracts, and obligations previously made or incurred by or in favor of any water district or sewer district, and all bonds or other obligations issued or executed by those districts, and all assessments or levies, and all other things and proceedings done or taken by those districts or by their respective officers, are declared legal and valid and of full force and effect.