Before issuing any bonds pursuant to this chapter, the board shall by resolution declare the purpose for which the proceeds of the bonds proposed to be issued shall be expended and shall specify the maximum amount of bonds to be issued or sold for that purpose. The bonds shall not be issued or sold for that purpose in an amount exceeding the specified maximum except with the consent of bondholders, pursuant to amendment or modification of an indenture, as provided in Section 81908. Nothing in this section shall be construed to prevent the board from amending any resolution prior to the issuance of bonds authorized thereby to increase or decrease the maximum amount of bonds to be issued or sold. The issuance of bonds for one or more projects may be included in a single resolution of authorization.