(a) All expenditures heretofore incurred, and all actions heretofore taken, by a drainage district for purposes authorized by this Chapter are hereby validated notwithstanding any defect in the selection of any or all of its commissioners or any other defect.
(b) The provisions of this section are expressly made applicable to any and all bonds and other financial obligations of any such district. No action based on the alleged invalidity of the assessments heretofore made or of any such bonds or other obligations of a district shall lie after January 1, 1991, to enjoin or contest the enforceability of any such assessment, bond, or other obligation.