Bonds of an authority shall be authorized by its resolution and may be issued in one or more series. The resolution, the trust indenture, or the mortgage shall provide for the bonds: a date or dates; the time or times of maturity; the interest rate or rates; the denomination or denominations; whether they will be in coupon or registered form; the conversion or registration privileges; their rank or priority; the manner of execution; the medium of payment; the place or places of payment; and the terms of redemption, with or without premium. Bonds may be sold at public or private sale in the manner and on the terms that a resolution of the authority authorizes. If a commissioner or officer of the authority whose signature is on a bond or coupon leaves office before the bond is delivered, the signature nevertheless is valid and sufficient, the same as if the commissioner or officer had remained in office until delivery. A bond reciting in substance that it has been issued by an authority to aid in financing a housing project to provide housing for persons of eligible income shall be considered to have been issued for that purpose in a proceeding involving the validity or enforceability of the bond or its security.