Every city officer before entering upon the duties of his or her office shall take and subscribe an oath, to be endorsed on his or her certificate of election or appointment before the Clerk-Treasurer or some other officer authorized to administer oaths, that he or she will support the Constitution of the United States and the Constitution of the state, and that he or she will faithfully discharge all of his or her official duties. The oath shall be filed with the Clerk-Treasurer.
(`94 Code, § 31.03)